374 Adjectives That Start with O | Best List Ever with Definitions and Examples

by Kimi

As you may know, adjectives that start with O are not as plentiful as those starting with other alphabets, such as A, B, and C. Nonetheless, they are equally significant and necessary in the English language. Adjectives that start with O are used to describe or enhance nouns and pronouns, making your writing and speech more particular and engaging.

If you lack confidence while speaking English, don’t worry. Here are several positive descriptive words that start with O. These adjectives that start with O will help you expand your vocabulary and improve your daily life conversation. They make you seem to be a well-educated individual. Speaking adjectives can enhance your mood as well as the moods of those around you.

We often use adjectives beginning with O in our everyday lives. Although learning new adjectives is crucial, understanding when and where to apply them is even more critical. It is more preferable to completely prohibit an adjective than to allow it in an inappropriate context.

The next challenge is determining whether adjectives beginning with O are being utilized in their true sense or not. Let’s look at some examples of adjectives that start with O.

Common Adjectives That Start with O

In this section, we explored some of the most common adjectives starting with O. Definitions, synonyms, and examples are given for these commonly used adjectives that start with O.

1. Optimum

  • Definition: which is most suitable and favorable under certain conditions
  • Synonyms: optimal, ideal, desirable
  • Example: The optimum body temperature of humans is 37°C.

2. Oblique

  • Definition: having a sloping direction, or position
  • Synonyms: slanting, slanted, sloping
  • Example: He sat on the settee oblique to the fireplace.

3. Ornamental

  • Definition: serving an esthetic or decorative purpose
  • Synonyms: decorative, fancy, exquisite
  • Example: He always takes pictures in front of his ornamental wall.

4. Optional

  • Definition: of personal will and choice
  • Synonyms: elective, voluntary, non-mandatory
  • Example: You have to select any two out of these five optional courses.

5. Overt

  • Definition: which is open and obvious to senses
  • Synonyms: open, clear, unexposed, undisguised
  • Example: He didn’t get must overt support for his suggestions.

6. Ordered

  • Definition: marked with a systematized arrangement or order
  • Synonyms: arranged, organized, classified
  • Example: He stacked his books in an ordered manner.

7. Opulent

  • Definition: displaying richness and splendor
  • Synonyms: luxurious, lavish, plush
  • Example: Shah Jehan built an opulent palace for his wife Mumtaz.

8. Original

  • Definition: of real and innovative character
  • Synonyms: real, authentic, genuine, actual
  • Example: You must present your original research work.

9. Obscure

  • Definition: not discovered or known
  • Synonyms: unclear, uncertain, unknown
  • Example: Her origin is obscure.

10. Organized

  • Definition: characterized by a structured arrangement
  • Synonyms: arranged, ordered, structured
  • Example: He belongs to a religiously organized group.

Positive Adjectives That Start with O

Positive adjectives that start with O can be found here. It is always vital to employ a positive adjective to describe someone or something to inspire or motivate others around you. Reading through these positive adjectives might help you improve your vocabulary.

1. Obedient

  • Definition: pertaining to obey orders, rules, and commands
  • Synonyms: docile, compliant, submissive
  • Example: He is an obedient officer.

2. Open-minded

  • Definition: having the quality of being perceptive and open to new ideas and opinions
  • Synonyms: broad-minded, unprejudiced, unbiased, liberal-minded
  • Example: Though he is a little strict boss, he is an open-minded investor.

3. Operational

  • Definition: of which is functional and in working order
  • Synonyms: operative, working, functional
  • Example: We must devise operational strategies to increase our exports.

4. Omnipresent

  • Definition: having existence everywhere simultaneously
  • Synonyms: ubiquitous, universal, prevalent, ever-present
  • Example: In today’s time, no bad deed can be hidden from the omnipresent media.

5. Objective

  • Definition: lacking any bias or partiality
  • Synonyms: unbiased, unprejudiced, neutral
  • Example: His objective judgments make him a good lawyer.

6. Opportune

  • Definition: which is fortunate at a particular time
  • Synonyms: auspicious, timely, advantageous
  • Example: She arrived at such an opportune moment.

7. Open-hearted

  • Definition: marked by displaying sympathy and kindness
  • Synonyms: sympathetic, generous, benignant
  • Example: He is a pure, honest, and open-hearted man.

8. Observable

  • Definition: which is capable of being observed and notices
  • Synonyms: noticeable, discernible, perceptible
  • Example: Everyone was appreciating the couple’s observable connection.

9. Ongoing

  • Definition: which is currently progressing and happening
  • Synonyms: continuing, progressive, advancing
  • Example: Responsible and respectful attitude is a key to an ongoing marital relation.

10. Omnipotent

  • Definition: capable of unlimited power and supremacy
  • Synonyms: almighty, all-powerful, invincible
  • Example: The youths of any nation are an omnipotent tool to bring a constructive change.

Adjectives That Start with O to Describe a Person

Please go through our list of adjectives that start with O to describe a person in the best way. Adjectives are used to describe one of a person’s most unique features. Please make use of them as much as possible.

1. Optimistic

  • Definition: characterized by hope and positive certainty
  • Synonyms: hopeful, positive, affirmative
  • Example: He always had optimistic remarks about the success of this project.

2. Orthodox

  • Definition: conforming to old norms and customs
  • Synonyms: conventional, traditional, conservative
  • Example: His grandfather is an orthodox man.

3. Overjoyed

  • Definition: feeling extremely joyful and pleasant
  • Synonyms: delighted, happy, joyful, elated
  • Example: Her overjoyed father hugged her tightly when she came from abroad after 3 years.

4. Odd

  • Definition: marked by peculiar behavior
  • Synonyms: strange, bizarre, weird, eccentric
  • Example: His odd behavior is getting out of control.

5. Outspoken

  • Definition: marked by straightforwardness and directness in action
  • Synonyms: blunt, candid, plain-spoken
  • Example: Mark is a very outspoken critic.

6. Outgoing

  • Definition: marked with the attributes of an extrovert
  • Synonyms: extroverted, friendly, sociable
  • Example: Karem has a big social circle because he is an outgoing person.

7. Odious

  • Definition: which is offensive and detestable
  • Synonyms: obnoxious, offensive, repulsive, abominable
  • Example: He is such an odious man who reveals others’ secrets.

8. Overfed

  • Definition: given and exceeding amount of food
  • Synonyms: glutted, stuffed, satiated,
  • Example: It may be possible that overfed people are actually undernourished.

9. Overweight

  • Definition: having more than average weight
  • Synonyms: obese, fleshy, heavy, corpulent
  • Example: The U.S. has the biggest number of overweight people.

10. Observant

  • Definition: quick to notice
  • Synonyms: alert, sharp-eyed, sharp
  • Example: She is very much observant.

Adjectives That Start with O to Describe Someone

The use of O words to describe someone is simple, yet the impact on readers or listeners is tremendous. You will notice how much more informed you feel after adding these describing words beginning with O that describe a person in your vocabulary.

1. Omniscient

  • Definition: knowing everything
  • Synonyms: all-knowing, all-wise, all-seeing
  • Example: She is an omniscient analyst.

2. Outstanding

  • Definition: of the highest attribute
  • Synonyms: excellent, great, remarkable
  • Example: He is an outstanding artist.

3. Outlandish

  • Definition: being unconventional and odd in conduct
  • Synonyms: bizarre, weird, unusual, strange
  • Example: He is an outlandish guy who wears pink skirts.

4. Obnoxious

  • Definition: which is offensive and detestable
  • Synonyms: offensive, odious, repulsive
  • Example: She is an obnoxious woman who gossips about others’ personal life in public.

5. Obtuse

  • Definition: annoyingly insensitive
  • Synonyms: stupid, dull, slow-witted
  • Example: He was deliberately being obtuse.

6. Outmoded

  • Definition: which is not acceptable by a majority
  • Synonyms: unacceptable, outdated, obsolete
  • Example: She was an outmoded girl in the house.

7. Officious

  • Definition: who is actively engaged in work
  • Synonyms: busy, engaged, occupied
  • Example: Her dad is an officious person and comes home late.

8. Opinionated

  • Definition: marked by stubbornness in opinions
  • Synonyms: dogmatic, prejudiced, obstinate
  • Example: The history teacher is a very opinionated person.

9. Obsessive

  • Definition: characterized by an obsession and psychological compulsion
  • Synonyms: compulsive, neurotic, fanatical, fixated
  • Example: Peter is an obsessive person.

10. Overexcited

  • Definition: marked by excessive excitement
  • Synonyms: hyper, frantic, agitated
  • Example: She suddenly became an overexcited fan after seeing her favorite singer.

Popular Adjectives That Start with O

In the list below, you will find popular adjective words that start with O that will assist you in making your speech more competent and clear in its meaning. This section delves into these well-known adjectives that start with the letter O, providing definitions and synonyms.

1. Overall

  • Definition: pertaining to everything and every aspect
  • Synonyms: generally, all-in-all, all-inclusive
  • Example: The overall result was good.

2. Overabundant

  • Definition: which is excessive and profuse
  • Synonyms: rife, plethoric, plentiful
  • Example: There were overabundant juice boxes in the refrigerator.

3. Operant

  • Definition: being active and producing effect
  • Synonyms: functioning, operative, working
  • Example: This is an operant agreement because all members have signed it.

4. Oral

  • Definition: being communicated through speech or words
  • Synonyms: spoken, verbal, vocal
  • Example: Oral agreements must be codified later.

5. Opaque

  • Definition: being hazy and difficult to comprehend
  • Synonyms: obscure, incomprehensible, unintelligible
  • Example: I couldn’t understand her opaque writing.

6. Ordinary

  • Definition: being usual in character
  • Synonyms: common, normal, average
  • Example: Passion makes ordinary people do extraordinary things.

7. Outbound

  • Definition: being extroverted and openly friendly
  • Synonyms: outgoing, outward, sociable
  • Example: He is an outbound person and has many friends.

8. Only

  • Definition: being just that and no more
  • Synonyms: merely, just, single
  • Example: He is the only child of this family.

9. Offbeat

  • Definition: which is not common and typical
  • Synonyms: unusual, unconventional, uncommon
  • Example: It’s hard to digest his offbeat performance.

10. Obligated

  • Definition: under an obligation
  • Synonyms: bound, obliged, beholden
  • Example: You are just doing an obligated service.

Useful List of Adjectives That Start with O

O adjectives can be found in our daily conversations and writings. This section offers a list of adjectives that start with O that we often use in our everyday lives.

1. Old

  • Definition: being of elderly age
  • Synonyms: aged, elderly, mature
  • Example: Though she is just 16 years, she thinks like an old person.

2. Oversized

  • Definition: bigger than the usual
  • Synonyms: bulging, floppy, droopy
  • Example: She has an oversized shirt.

3. Oily

  • Definition: containing oil
  • Synonyms: greasy, fatty, buttery
  • Example: She has oily skin.

4. Obliging

  • Definition: disposed to obligation and accommodation
  • Synonyms: cooperative, compliant, accommodating
  • Example: Sarah is an obliging employee.

5. Oblong

  • Definition: having an ovate shape
  • Synonyms: oval, elongated, elliptical
  • Example: The blue oblong tablets must be taken in the morning.

6. Odorless

  • Definition: without an odor to be sensed by nose
  • Synonyms: scentless, fragrance-free, inodorous
  • Example: Many odorless gases are toxic to health.

7. Oblivious

  • Definition: being inattentive and negligent
  • Synonyms: heedless, unaware, unmindful
  • Example: They are not happy with this oblivious solicitor.

8. Overzealous

  • Definition: too enthusiastic and eager
  • Synonyms: overeager, bossy, enthusiastic
  • Example: There were overzealous fans in the stadium.

9. Obvious

  • Definition: which is apparent and clear
  • Synonyms: evident, clear, plain
  • Example: There was an obvious birthmark on her face.

10. Occupied

  • Definition: being busy with some thing
  • Synonyms: immersed, engrossed, engaged
  • Example: The guests need to wait to meet the occupied manager.

Negative Adjectives That Start with O

Here is a list of negative adjectives that start with O. Not every noun modification is positive. Some of them make people think of sad, unpleasant, or undesired situations. There are negative adjectives with letter O.

1. Obese

  • Definition: having excessive fat and weight of body
  • Synonyms: corpulent, fleshy, fat, overweight
  • Example: The West has the greatest number of obese children.

2. Obsolete

  • Definition: out of the trend and norm
  • Synonyms: outdated, outmoded, out-of-date
  • Example: You can’t find any information in this obsolete encyclopedia.

3. Obscene

  • Definition: offensive or shocking
  • Synonyms: shocking, scandalous, vile
  • Example: She always uses obscene language.

4. Offensive

  • Definition: marked by insult and repulsion
  • Synonyms: repulsive, ridiculing, obnoxious
  • Example: His offensive remarks made her lose her confidence.

5. Oppressive

  • Definition: marked by the attributes of tyranny and brutality
  • Synonyms: dictatorial, autocratic, tyrannical
  • Example: Everyone is scared from this oppressive king.

6. Odoriferous

  • Definition: having a smell
  • Synonyms: aromatic, pungent, savory
  • Example: They have an odoriferous pile of fish.

7. Overburdened

  • Definition: being excessively burdened
  • Synonyms: overloaded, overworked, burdened
  • Example: After her husband’s death, she is now living an overburdened life.

8. Overactive

  • Definition: characterized by an action which is more than normal
  • Synonyms: frenzied, hyperactive, frantic
  • Example: An overactive thyroid can make you overweight.

9. Outdated

  • Definition: which is not in date or trend
  • Synonyms: obsolete, outmoded, old
  • Example: You can’t find the desired information in this outdated database.

10. Outrageous

  • Definition: being in extreme rage and dread
  • Synonyms: atrocious, dreadful, abominable
  • Example: You have hurt her with your outrageous behavior.

More Adjectives That Start with O

Here are some adjectives that start with O that are often used in daily discussions. How many of these descriptive words beginning with O, do you use in everyday speech and writing?

1. Obstinate

  • Definition: directed by an unwillingness to change
  • Synonyms: stubborn, headstrong, inflexible
  • Example: She is an obstinate person.

2. Obtrusive

  • Definition: being prominent in a nosy manner
  • Synonyms: intrusive, meddlesome, interfering
  • Example: She always gives obtrusive plans.

3. Opposite

  • Definition: marked with a sheer difference and contrast
  • Synonyms: contrary, reverse, opposing
  • Example: This is a totally opposite idea.

4. Obdurate

  • Definition: marked by a stubbornness in not changing own ideas and opinions
  • Synonyms: headstrong, obstinate, intransigent
  • Example: She could not precede this discussion because of her obdurate opinions.

5. Ornate

  • Definition: marked by an extravagance in an ornamental way
  • Synonyms: fancy, flamboyant, decorative
  • Example: She bought an ornate lamp from China.

6. Oafish

  • Definition: marked with rudeness and clumsiness in behavior
  • Synonyms: clumsy, stupid, awkward
  • Example: This team is led by an oafish person.

7. Occurrent

  • Definition: being in actual existence or occurrence
  • Synonyms: occurring, happening, current
  • Example: You must read about the occurrent political events to understand the issue.

8. Online

  • Definition: being on internet and digital space
  • Synonyms: virtual, web-based, electronically
  • Example: Everyone is taking online classes these days.

9. Onetime

  • Definition: pertaining to just one time
  • Synonyms: once, only, original
  • Example: This is a onetime chance to avail this opportunity.

10. Opaline

  • Definition: marked with the features of opal
  • Synonyms: opalescent, nacreous, iridescent
  • Example: She likes to buy decorative pieces made of opaline glass.

Adjectives That Start with O – Full List (374 Words)

Now that you’ve done reading the adjectives beginning with the letter O, it’s time to go over your notes again. The following is a thorough list of adjectives that start with O introduced above as well as other O adjectives.

  • Optional
  • Ovoid
  • Operable
  • Organisational
  • Overrated
  • Outdoor
  • Oleaceous
  • Outermost
  • Occasional
  • Otherworldly
  • Objective
  • Offside
  • Overgrown
  • Outre
  • Outmost
  • Operatic
  • Oceanic
  • Ontogenetic
  • Overjoyed
  • Overactive
  • Overall
  • Ossified
  • Occluded
  • Olive
  • Orotund
  • Odiferous
  • Oversized
  • Oozy
  • Overindulgent
  • Offbeat
  • Ocellated
  • Overladen
  • Orgiastic
  • Operative
  • Overnice
  • Overfed
  • Oratorical
  • Omnivorous
  • Overwhelmed
  • Opalescent
  • Outboard
  • Otic
  • Organic
  • Observational
  • Open-hearted
  • Overcurious
  • Outstretched
  • Ornamental
  • Oversexed
  • Opportune
  • Operculate
  • Occlusive
  • Orphic
  • Ordained
  • Overfamiliar
  • Odorous
  • Outstanding
  • Officious
  • Operating
  • Own
  • Overfull
  • Oldline
  • Oscitant
  • Ovine
  • Open-minded
  • Opaline
  • Osseous
  • Optic
  • Ovoviviparous
  • Organised
  • One
  • Other
  • Otiose
  • Opposed
  • Outlying
  • Ominous
  • Outrigged
  • Ornate
  • Optimistic
  • Obsolescent
  • Overbearing
  • Organizational
  • Ornithological
  • Overwrought
  • Ophthalmic
  • Opencut
  • Overambitious
  • Obstructed
  • Obsequious
  • Observing
  • Overland
  • Ordinary
  • Observant
  • Optimal
  • Obligational
  • Optative
  • Overpriced
  • Occurrent
  • Overgenerous
  • Obliterated
  • Overproud
  • Ohmic
  • Omnipresent
  • Opulent
  • Omnipotent
  • Opposing
  • Orangish
  • Olympian
  • Orbiculate
  • Octuple
  • Occidental
  • Outdated
  • Overwhelming
  • Oversolicitous
  • Opening
  • Observable
  • Oppositive
  • Outcast
  • Offensive
  • Orthopedic
  • Overaged
  • Oligarchic
  • Obsessional
  • Outer
  • Oval
  • Outrageous
  • Overdressed
  • Operculated
  • Outbred
  • Online
  • Oscine
  • Originative
  • Oblong
  • Orange
  • Overoptimistic
  • Overconfident
  • Opposite
  • Overt
  • Offended
  • Ornery
  • Olfactory
  • Opportunistic
  • Outside
  • Ovate
  • Over
  • Off
  • Onymous
  • Overstrung
  • Onomastic
  • Oviform
  • Olden
  • Open-handed
  • Orchestral
  • Obstetrical
  • Orwellian
  • Orthotropous
  • Oropharyngeal
  • Overdelicate
  • Obscene
  • Oxidizable
  • Oncoming
  • Overzealous
  • Oxidised
  • Ownerless
  • Overjealous
  • Original
  • Oleophilic
  • Orderly
  • Obstreperous
  • Operose
  • Overprotective
  • Obtuse
  • Outward
  • Orbitual
  • Overcautious
  • Orbicular
  • Oversewn
  • Oblique
  • Orphaned
  • Opposable
  • Ovarian
  • Oceangoing
  • Orthostatic
  • Openhearted
  • Overcooked
  • Overweening
  • Overmuch
  • Openhanded
  • Overqualified
  • Oriental
  • Outlandish
  • Opinionative
  • Olfactive
  • Operant
  • Overweight
  • Outflowing
  • Overburdened
  • Organismal
  • Ongoing
  • Overcareful
  • Overanxious
  • Omnidirectional
  • Obliterable
  • Overripe
  • Openmouthed
  • Occupied
  • Onshore
  • Overrefined
  • Old-fashioned
  • Omissible
  • Offenseless
  • Offshore
  • Opaque
  • Overcritical
  • Oneiric
  • Overbusy
  • Obliterate
  • Overheated
  • Overcrowded
  • Obedient
  • Oviparous
  • Oblivious
  • Odourless
  • Orthopaedic
  • Ossiferous
  • Osteal
  • Overbold
  • Omissive
  • Offhanded
  • Overgreedy
  • Overhand
  • Overabundant
  • Octosyllabic
  • Offhand
  • Oversubscribed
  • Obligatory
  • Outclassed
  • Offstage
  • Outspread
  • Obnoxious
  • Overseas
  • Onside
  • Ordinal
  • Overenthusiastic
  • Obliging
  • Onstage
  • Organicistic
  • Oaken
  • Overserious
  • Oversize
  • Overlying
  • Offish
  • Oddish
  • Outgoing
  • Odd
  • Obdurate
  • Obtainable
  • Occult
  • Official
  • Opencast
  • Oleophobic
  • Oblate
  • Outbound
  • Outcaste
  • Oecumenical
  • Oppressive
  • Overcast
  • Oily
  • Owing
  • Odoriferous
  • Overlarge
  • Owned
  • Omnifarious
  • Ostentatious
  • Olivelike
  • Orthoptic
  • Ottoman
  • Oversea
  • Ototoxic
  • Optimum
  • Outlaw
  • Orthodox
  • Outmoded
  • Ocher
  • Overworked
  • Overmodest
  • Oblanceolate
  • Old
  • Odorless
  • Obstetric
  • Orthomolecular
  • Overpowering
  • Overblown
  • Orthogonal
  • Oversensitive
  • Overexcited
  • Obovate
  • Octogenarian
  • Overnight
  • Oxidative
  • Outback
  • Octangular
  • Obligated
  • Ossiculate
  • Organismic
  • Opprobrious
  • Outraged
  • Orientated
  • Obtrusive
  • Overcredulous
  • Octal
  • Overarm
  • Ontological
  • OK
  • Overstuffed
  • Obsessive
  • Overaggressive
  • Only
  • Omani
  • Oncologic
  • Onetime
  • Overshot
  • Ochre
  • Obstructive
  • Orthopedical
  • Obscure
  • Oversuspicious
  • Obligate
  • Organized
  • Obstinate
  • Optical
  • Oaten
  • Oecumenic
  • Ostensive
  • Obvious
  • Oldish
  • Opinionated
  • Outsized
  • Onerous
  • Oafish
  • Outspoken
  • Occipital
  • Owlish
  • Octagonal
  • Overhasty
  • Objectionable
  • Occupational
  • Ostensible
  • Overvaliant
  • Overfond
  • Obese
  • Opponent
  • Otherwise
  • Oleaginous
  • Ossicular
  • Ocular
  • Outlawed
  • Overhead
  • Omnibus
  • Open
  • Oriented
  • Oracular
  • Operational
  • Obsolete
  • Overemotional
  • Olympic
  • Orbital
  • Odious
  • Overdue
  • Oral
  • Outright
  • Overhanded
  • Omniscient
  • Ordered

Final Thoughts on Adjectives That Start with O

Nouns are one of the most significant parts of speech in general. Descriptive words that start with O, on the other hand, make your speech more precise and comprehensible. The issue with adjectives is that you never want to use too many of them. An overabundance of adjectives may clog up a phrase, decreasing its fluency. Remember to use these adjectives starting with O only when necessary.

Do you like these adjectives that start with O that we compiled for you? We hope you find them beneficial. When you start employing them in talks, you will feel more competent and confident about yourself.

Share this with friends and family if you think it will help them. You will be able to inculcate these adjectives in your life if you study them again and again. We hope you liked this collection of adjectives that start with O.

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