Few things in life offer such perfection as the letter “O.” It’s a perfect circle, an outstanding shape that forms some of the most optimal adjectives you’ll ever see. Adjectives are that special ingredient that help nouns become more opulent, ostentatious, or just plain ordinary. Adjectives that start with “O” give you an overflowing amount of options for your everyday vocabulary.
Positive Adjectives That Start With “O”
“O” adjectives offer a whole spectrum of positivity for you to play with. Are you having an okay time or an outstanding time? With the right positive adjective, your jewelry can be ornate or opalescent, and you can be more optimistic and outgoing.
| Adjective | Definition | Synonyms |
| obliging | ready to do favors; helpful; courteous; accommodating | friendly, amiable, hospitable |
| observant | quick to notice or perceive | alert, watchful, careful |
| odds-on | having a strong chance of succeeding or winning | favorite, predictable, likely |
| okay (or OK) | correct; meeting standards; proceeding normally | satisfactory, acceptable |
| omnicompetent | able to deal with all matters or situations | multitalented, capable, efficient |
| one-of-a-kind | unique | original, distinct, rare |
| opalescent | displaying a variety of colors, like an opal | iridescent, prismatic, multi-colored |
| open-hearted | not reserved; kindly or benevolent | compassionate, friendly, generous |
| open-minded | unbiased; consider new ideas | receptive, approachable, understanding |
| opportune | happening or done at the right time; seasonable; well-timed; timely | advantageous, auspicious, felicitous |
| optimal | best; most favorable | excellent, greatest, matchless |
| optimistic | having the tendency to take the most hopeful or cheerful view of matters or to expect the best outcome | positive, hopeful, idealistic |
| optimum | best; most favorable | ideal, greatest, superlative |
| opulent | very wealthy or rich; characterized by abundance | extravagant, luxurious, lavish |
| orderly | organized in a neat, tidy manner | systematic, clean, well-kept |
| originative | having the power to produce or create something | creative, gifted, innovative |
| ornate | elaborate; embellished | baroque, elegant, lavish |
| orotund | (of voice or speech) strong, full, rich, and clear | bombastic, resonant, sonorous |
| outgoing | friendly, sociable | extroverted, warm, gregarious |
| out-of-this-world | superb, extraordinary | marvelous, heavenly, wonderful |
| outstanding | prominent; distinguished; excellent; marked by superiority or distinction | exceptional, impressive, magnificent |
| overjoyed | extremely happy; delighted | joyful, euphoric, jubilant |
Negative Adjectives That Start With “O”
Unfortunately, not all moments call for positivity. Sometimes, you need a negative adjective starting with “O” to describe any objectionable offenses, obscene occasions, or odious occurrences.
| Adjective | Definition | Synonyms |
| objectionable | disagreeable; offensive | unpleasant, deplorable, repulsive |
| oblique | slanting; indirectly stated or expressed; evasive | backhanded, vague, sideways |
| obliterated | destroyed utterly | eliminated, annihilated, erased |
| oblivious | not aware of or concerned; unmindful; forgetful | unconscious, unaware, ignorant |
| obnoxious | very unpleasant | offensive, detestable, hateful |
| obscene | offensive to one's feelings, or to prevailing notions of modesty or decency; lewd | indecent, bawdy, crude |
| obscure | not clear; uncertain | confusing, enigmatic, ambiguous |
| obstinate | stubbornly adhering to one’s opinion | inflexible, dogmatic, headstrong |
| obstructive | blocking, hindering, or interrupting; deliberately causing delays | unhelpful, difficult, unaccommodating |
| obtrusive | noticeable in an intrusive or unwelcome way | obvious, meddlesome, intrusive |
| obtuse | slow to understand or perceive; dull or insensitive | blunt, dense, imperceptive |
| odious | repulsive; revolting | horrible, loathsome, vile |
| offensive | unpleasant to the senses; disgusting | repugnant, irritating, objectonable |
| officious | aggressive in offering unwanted services or help; asserting authority in a domineering way | bossy, meddlesome, pushy |
| ominous | portending harm or evil | foreboding, inauspicious, menacing |
| onerous | involving a great amount of effort that can feel oppressively burdensome | arduous, exhausting, laborious |
| opinionated | stubborn or conceited in regard to the merits of one’s opinions | dogmatic, co*cky, bullheaded |
| opportunistic | taking advantage of the situation for personal benefit | conniving, wily, devious |
| oppressive | unjust treatment; cruel; tyrannical | overwhelming, burdensome, inhuman |
| ostentatious | characterized by or given to pretentious or conspicuous show in an attempt to impress others | gaudy, highfalutin, egotistic |
| overbearing | overpowering or domineering | bossy, imperious, oppressive |
| overblown | overinflated; excessive | pretentious, disproportionate, turgid |
| overloaded | loaded with an excessive burden | overworked, strained, stressed |
| oversimplified | simplified to the point of misrepresenting facts | simplistic, unnuanced, distorted |
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Neutral Adjectives That Start With “O”
Of course, most of life isn’t just positive or negative. Most people, places, and objects just exist, but that doesn’t mean they should go without some good descriptors. From odd cookies to omnivorous bears, “O” adjectives offer plenty of optional ornaments for your nouns.
| Adjective | Definition | Synonyms |
| obese | fat; stout | corpulent, plump, portly |
| obsolete | no longer in use or practice; discarded | antiquated, dated, archaic |
| obvious | clear; apparent | understandable, overt, noticeable |
| occasional | of irregular occurrence; happening now and then | sporadic, intermittent, infrequent |
| odd | not usual or ordinary; singular; peculiar; strange | different, unusual, bizarre |
| offbeat | unusual | strange, unconventional, idiosyncratic |
| oily | of, like, consisting of, or containing oil; smooth or unctuous in character or manner | slippery, buttery, slick |
| older | not young; lived for a long time | elder, senior |
| old-fashioned | behind the times; not current | antiquated, dated, outmoded |
| omnipotent | having unlimited power or authority; all-powerful | almighty, godlike, unrestricted |
| omniscient | having infinite knowledge; knowing all things | all-know, all-seeing, pansophical |
| omnivorous | eating both plants and animals; taking in everything | predatory, ravenous, gluttonous |
| opaque | not letting light pass through; not transparent or translucent | cloudy, hazy, murky |
| operable | usable; can be used | feasible, doable, practicable |
| operative | functioning; effective | active, usable, functional |
| opposing/opposed | set against; placed opposite, in balance or contrast; contending within speech or action | resisting, antagonistic, conflicting |
| opposable | (of thumbs) capable of touching other digits on hand | prehensile |
| opposite | different in every way; exactly contrary | antithetical, unlike, contradictory |
| optional | not required; left to your own choice | noncompulsory, nonobligatory, discretional |
| oral | spoken by the mouth | vocal, articulate, phonated |
| orange | color between red and yellow | red-yellow, carrot |
| ordinary | not special; normal; usual | everyday, typical, common |
| original | having to do with an origin; fresh, new, novel | initial, creative, earliest |
| ornamental | decorative | showy, dressy, embellishing |
| orthodox | conforming to the usual beliefs or established doctrines, as in religion, politics, etc. | traditional, conventional, conservative |
| outlandish | bizarre; unfamiliar; weird | strange, eccentric, peculiar |
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“O” Adjectives To Describe a Person
Plenty of the adjectives above offer some excellent, obvious descriptors for people, but it doesn’t hurt to arm yourself with plenty of official “O” adjectives to describe a person.
| Adjective | Definition | Synonyms |
| oafish | clumsy; uncultured | blundering, bumbling, graceless |
| obedient | obeying or willing to obey; submissive | well-behaved, compliant, faithful |
| obeisant | showing respect | deferential, reverent, dutiful |
| obsessive | consuming; being consumed | compulsive, controlling, fanatical |
| occupied | active or busy | engrossed, engaged, employed |
| ornery | stubborn; unpleasant in disposition or temper | cranky, grumpy, ill-tempered |
| outcast | rejected or discarded; cast out | unwanted, unaccepted, undesirable |
| outdoorsy | extremely fond of outdoor life | nature-loving |
| outrageous | having the nature of, involving, or doing great injury or wrong; very offensive or shocking | disgraceful, scandalous, startling |
| outspoken | express opinions directly; blunt | candid, forthright, frank |
| overachieving | performing better or accomplishing more than expected | outperforming, intellectual, phenomenal |
| overbold | excessively bold | blatant, conspicuous, shameless |
| overconfident | extremely confident | brash, careless, co*cky |
| overcritical | extremely critical | hypercritical, nit-picking, disparaging |
| overextended | exhausted; stressed out | fatigued, overworked, burdened |
| overprotective | excessively protective | vigilant, shielding, restrictive |
| overqualified | having more experience, training, or education than required for a job or position | worldly, scholarly, well-read |
| overwrought | extremely excited or agitated | frantic, emotional, worked-up |
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Example Sentences for Adjectives That Start With “O”
Knowing all these adjectives that start with “O” is just half the battle. You have to learn how to actually use them until you feel overconfident and overqualified.
- My open-minded friend was willing to try just about anything at least once.
- I had the onerous task of alphabetizing all of our spices and condiments.
- She made a one-of-a-kind mug in her ceramics class.
- Despite his offbeat personality, he was extremely relatable and easy to get along with.
- He was ashamed of the glass cup that had gotten increasingly opaque from sitting on his desk for so long.
- After weeks of being under construction, the elevator was finally operable.
- The obnoxious combination of screaming kids and someone practicing the bagpipes made it hard for him to get any rest.
- He was worried about the ominous work email that simply read, “Do you have time to talk?”
- Aside from the occasional pepperoni pizza, his diet was mostly vegetarian.
- The oppressive heat made it hard for her to want to do anything other than read in an air-conditioned cafe.
- The French fries were oily, but that’s exactly how he liked them.
- Our outgoing friend was always talking to strangers and making friends with store workers.
- This seemed like an opportune moment to remind the kids not to push and shove each other when the bell rang.
- The final exam involved a written test and an oral presentation.
- Whenever he felt himself losing hope, he talked to his optimistic friend.
- She appreciated the fine artistry and ornate details in the statue.
- The camp ranger taught us about the omnivorous bears that loved to eat meat, roots, and marshmallows.
- The overjoyed team learnedthey had two days off this week.
- The whole class did such an outstanding job on the test that she told them they’d have pizza and ice cream to celebrate.
- They spent two hours discussing the optimum amount of salsa for tortilla chips.
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Oh! Even More “O” Words
With your brain overloaded with adjectives starting with “O,” you can expand your vocabulary further with other parts of speech. Learning more words that start with “O” will improve your writing and conversational abilities, and it just might help you get the winning score in your word games.
- Nouns That Start With “O”
- Verbs That Start With “O”
- “O” Words for Word Games
