Words beginning with O - list and definitions learning English
What will I learn from the English lesson a list verbs beginning with O?
This lesson is a list of words beginning with O from the big list of A to Z of words and definitions to help you, when you don't know the meaning of the word. It is important not to try and remember the words, but just to use the list as a reference guide to help you.
How do I use this English book of words A to Z?
Click on each letter of the alphabet to get the list of the idioms with an explanation of each.
[ A ] [ B ] [ C ] [ D ] [ E ] [ F ] [ G ] [ H ] [ I ] [ J ] [ K ] [ L ] [ M ] [ N ] [ O ] [ P ] [ Q ] [ R ] [ S ] [ T ] [ U ] [ V ] [ W ] [ X ] [ Y ] [ Z ]
The big book of words uses the following grammar after each word
After each word is listed you will see one of the following v, n or adj. To get a more detailed explanation of each click on each link.
- n. (noun) - is a name word
- v. (verb) - is an action word
- ad. (adjective/adverb) - is used as a describing word
Words Beginning with O.
oakum n. Hemp-fiber obtained by untwisting and picking out loosely the yarns of old hemp rope.
obdurate adj. Impassive to feelings of humanity or pity.
obelisk n. A square shaft with pyramidal top, usually monumental or commemorative.
obese adj. Exceedingly fat.
obesity n. Excessive fatness.
obituary adj. A published notice of a death.
objective adj. Grasping and representing facts as they are.
objector n. One who objects, as to a proposition, measure, or ruling.
obligate v. To hold to the fulfillment of duty.
obligatory adj. Binding in law or conscience.
oblique adj. Slanting; said of lines.
obliterate v. To cause to disappear.
oblivion n. The state of having passed out of the memory or of being utterly forgotten.
oblong adj. Longer than broad: applied most commonly to rectangular objects considerably elongated
obnoxious adj. Detestable.
obsequies n. Funeral rites.
obsequious adj. Showing a servile readiness to fall in with the wishes or will of another.
observance n. A traditional form or customary act.
observant adj. Quick to notice.
observatory n. A building designed for systematic astronomical observations.
obsolescence n. The condition or process of gradually falling into disuse.
obsolescent adj. Passing out of use, as a word.
obsolete adj. No longer practiced or accepted.
obstetrician n. A practitioner of midwifery.
obstetrics n. The branch of medical science concerned with the treatment and care of women during pregnancy.
obstinacy n. Stubborn adherence to opinion, arising from conceit or the desire to have one's own way.
obstreperous adj. Boisterous.
obstruct v. To fill with impediments so as to prevent passage, either wholly or in part.
obstruction n. Hindrance.
obtrude v. To be pushed or to push oneself into undue prominence.
obtrusive adj. Tending to be pushed or to push oneself into undue prominence.
obvert v. To turn the front or principal side of (a thing) toward any person or object.
obviate v. To clear away or provide for, as an objection or difficulty.
occasion n. An important event or celebration.
Occident n. The countries lying west of Asia and the Turkish dominions.
occlude v. To absorb, as a gas by a metal.
occult adj. Existing but not immediately perceptible.
occupant n. A tenant in possession of property, as distinguished from the actual owner.
occurrence n. A happening.
octagon n. A figure with eight sides and eight angles.
octave n. A note at this interval above or below any other, considered in relation to that other.
octavo n. A book, or collection of paper in which the sheets are so folded as to make eight leaves.
octogenarian adj. A person of between eighty and ninety years.
ocular adj. Of or pertaining to the eye.
oculist n. One versed or skilled in treating diseases of the eye.
oddity n. An eccentricity.
ode n. The form of lyric poetry anciently intended to be sung.
odious adj. Hateful.
odium n. A feeling of extreme repugnance, or of dislike and disgust.
odoriferous adj. Having or diffusing an odor or scent, especially an agreeable one.
odorous adj. Having an odor, especially a fragrant one.
off adj. Farther or more distant.
offhand adv. Without preparation.
officiate v. To act as an officer or leader.
officious adj. Intermeddling with what is not one's concern.
offshoot n. Something that branches off from the parent stock.
ogre n. A demon or monster that was supposed to devour human beings.
ointment n. A fatty preparation with a butter-like consistency in which a medicinal substance exists.
olfactory adj. of or pertaining to the sense of smell.
olive-branch n. A branch of the olive-tree, as an emblem of peace.
ominous adj. Portentous.
omission n. Exclusion.
omnipotence n. Unlimited and universal power.
Omnipotent adj. Possessed of unlimited and universal power.
omniscience n. Unlimited or infinite knowledge.
omniscient adj. Characterized by unlimited or infinite knowledge.
omnivorous adj. Eating or living upon food of all kinds indiscriminately.
onerous adj. Burdensome or oppressive.
onrush n. Onset.
onset n. An assault, especially of troops, upon an enemy or fortification.
onslaught n. A violent onset.
onus n. A burden or responsibility.
opalescence n. The property of combined refraction and reflection of light, resulting in smoky tints.
opaque adj. Impervious to light.
operate v. To put in action and supervise the working of.
operative adj. Active.
operator n. One who works with or controls some machine or scientific apparatus.
operetta n. A humorous play in dialogue and music, of more than one act.
opinion n. A conclusion or judgment held with confidence, but falling short of positive knowledge.
opponent n. One who supports the opposite side in a debate, discussion, struggle, or sport.
opportune adj. Especially fit as occurring, said, or done at the right moment.
opportunist n. One who takes advantage of circumstances to gain his ends.
opportunity n. Favorable or advantageous chance or opening.
opposite adj. Radically different or contrary in action or movement.
opprobrium n. The state of being scornfully reproached or accused of evil.
optic n. Pertaining to the eye or vision.
optician n. One who makes or deals in optical instruments or eye-glasses.
optics n. The science that treats of light and vision, and all that is connected with sight.
optimism n. The view that everything in nature and the history of mankind is ordered for the best.
option n. The right, power, or liberty of choosing.
optometry n. Measurement of the powers of vision.
opulence n. Affluence.
opulent adj. Wealthy.
oral adj. Uttered through the mouth.
orate v. To deliver an elaborate or formal public speech.
oration n. An elaborate or formal public speech.
orator n. One who delivers an elaborate or formal speech.
oratorio n. A composition for solo voices, chorus, and orchestra, generally taken from the scriptures.
oratory n. The art of public speaking.
ordeal n. Anything that severely tests courage, strength, patience, conscience, etc.
ordinal n. That form of the numeral that shows the order of anything in a series, as first, second, third.
ordination n. A consecration to the ministry.
ordnance n. A general name for all kinds of weapons and their appliances used in war.
orgies n. Wild or wanton revelry.
origin n. The beginning of that which becomes or is made to be.
original adj. Not copied nor produced by imitation.
originate v. To cause or constitute the beginning or first stage of the existence of.
ornate adj. Ornamented to a marked degree.
orthodox adj. Holding the commonly accepted faith.
orthodoxy n. Acceptance of the common faith.
orthogonal adj. Having or determined by right angles.
orthopedic adj. Relating to the correcting or preventing of deformity
orthopedist n. One who practices the correcting or preventing of deformity
oscillate v. To swing back and forth.
osculate v. To kiss.
ossify v. to convert into bone.
ostentation n. A display dictated by vanity and intended to invite applause or flattery.
ostracism n. Exclusion from intercourse or favor, as in society or politics.
ostracize v. To exclude from public or private favor.
ought v. To be under moral obligation to be or do.
oust v. To eject.
out-and-out adv. Genuinely.
outbreak n. A sudden and violent breaking forth, as of something that has been pent up or restrained.
outburst n. A violent issue, especially of passion in an individual.
outcast n. One rejected and despised, especially socially.
outcry n. A vehement or loud cry or clamor.
outdo v. To surpass.
outlandish adj. Of barbarous, uncouth, and unfamiliar aspect or action.
outlast v. To last longer than.
outlaw n. A habitual lawbreaker.
outlive v. To continue to exist after.
out-of-the-way adj. Remotely situated.
outpost n. A detachment of troops stationed at a distance from the main body to guard against surprise.
outrage n. A gross infringement of morality or decency.
outrageous adj. Shocking in conduct.
outreach v. To reach or go beyond.
outride v. To ride faster than.
outrigger n. A part built or arranged to project beyond a natural outline for support.
outright adv. Entirely.
outskirt n. A border region.
outstretch v. To extend.
outstrip v. To go beyond.
outweigh v. To surpass in importance or excellence.
overdo v. To overtax the strength of.
overdose n. An excessive dose, usually so large a dose of a medicine that its effect is toxic.
overeat v. To eat to excess.
overhang n. A portion of a structure which projects or hangs over.
overleap v. To leap beyond.
overlord n. One who holds supremacy over another.
overpass v. To pass across or over, as a river.
overpay v. To pay or reward in excess.
overpower v. To gain supremacy or victory over by superior power.
overproduction n. Excessive production.
overreach v. To stretch out too far.
overrun v. To infest or ravage.
oversee v. To superintend.
overseer n. A supervisor.
overshadow v. To cast into the shade or render insignificant by comparison.
overstride v. To step beyond.
overthrow v. To vanquish an established ruler or government.
overtone n. A harmonic.
overture n. An instrumental prelude to an opera, oratorio, or ballet.
overweight n. Preponderance.
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