On all fours, 1. On lour legs.

2. Evenly balanced, quite parallel, quite symmetrical.

On all hands, By all parties, by everybody.

On an average, Taking a mean of all cases, taking the average.

Onanism, n. Masturbation, self-pollution, self-abuse, secret vice.

On a par, On a level, on an equality.

Once, ad. 1. For one time.

2. Formerly, in former times.

On-dit, n. [Fr.] Rumor, report, bruit, the town talk, flying report.

One, a. 1. Single, individual.

2. The same.

3. United, undivided.

One, n. 1. Unit.

2. Individual, person, human being.

One-berry, n. True-love, herb-paris (Paris quadrifolia).

One day, Some day, sooner or later, one of these days.

On end, Erect, upright.

One of these days, Some day, one day, sooner or later.

Onerous, a. Burdensome, oppressive, heavy, weighty, laborious, toilsome, operose, hard, difficult.

On exhibition, Displayed, exhibited, on view.

On hand, In possession, in store.

On horseback, On a horse's back, riding a horse.

On-looker, n. Spectator, beholder, observer, by-stander, looker-on.

Only, a. Sole, solitary, alone, single, this and no other.

Only, ad. 1. Merely, barely, simply, and nothing else.

2. Solely, singly.

On one's own hook, [Colloquial, U. S.] On one's own account, by one's self.

On the qui vive, On the alert.

On sale, For sale, to be sold, offered for sale.

Onset, n. Attack, assault, charge, storm, storming, first brunt.

Onslaught, n. Attack, assault, charge, storm, storming, first brunt.

On stilts, Pretentious, pompous, bombastic.

On tap, Tapped, broached, abroach.

On the alert, Watching, watchful, attentive, vigilant, on the look out.

On the anvil, In preparation, in progress, in process.

On the contrary, 1. In opposition, on the other side.

2. So far from being so it is just the reverse, it is quite otherwise.

On the docket, [Colloquial.] In hand, under consideration.

On the look out, Watchful, on the alert.

On the mending hand, Convalescent, getting better.

On the passage, On the way (especially by sea), en route.

On the score of, On account of.

On the sly, [Colloquial.] Furtively, slyly.

On the spot, Immediately, at once, upon the spot.

On the way, On the passage, en route.

On the whole, All things considered, in view of all the circumstances, taking every thing into account, upon the whole.

On the wing, Flying.

On tick, [Colloquial.] On credit.

On view, On exhibition.

Onward, ad. Forward, in advance.

Onwards, ad. Forward, in advance.

Oolite, n. Roestone.

Ooze, n. Mire, slime, mud.

Ooze, v. n. Percolate, filter, transude, exude, strain.

Oozy, a. Miry, slimy, muddy.

Opacity, n. Opaqueness, want of transparency.

Opaque, a. Not transparent.

Opaqueness, n. Opacity, want of transparency.

Ope, v. a. & n. [Poetical.] Open.

Open, v. a. 1. Unclose, ope, lay open.

2. Exhibit, explain, reveal, interpret, disclose, make manifest, bring to view.

3. Begin, commence, enter upon.

Open, v. n. 1. Ope, cleave, part, be unclosed, be parted, be sundered, be severed.

2. Come into view, begin to appear.

3. Begin, commence.

Open, a. 1. Unclosed, not shut.

2. Expanded, extended, broad, not folded, not contracted.

3. Frank, unreserved, candid, ingenuous, undisguised, undesigning, artless, undissembling, sincere, guileless, fair, honest, single-minded, above-board, open-hearted.

4. Liberal, generous, munificent, bountiful, open-handed.

5. Exposed, unprotected, undefended.

6. Public, unrestricted, clear, unobstructed, free to all.

7. Unsettled, undetermined, not adjusted.

8. Mild, moderate, not frosty, not cold.

Open-handed, a. Generous, liberal, munificent, bountiful.

Open-hearted, a. Candid, frank, artless, guileless, open.

Opening, n. 1. Aperture, hole, orifice, perforation, breach, chasm, cleft, gap, fissure, rent, rift, flaw.

2. Beginning, commencement.

3. Opportunity, chance.

Opera-glass, n. Lorgnette.

Operate, v. n. [Followed by on or upon.] Act, work, have effect, have influence.

Operation, n. 1. Action, agency, force, influence, effect.

2. Performance, procedure, process, proceeding, manipulation.

3. Movement, motion, manœuvre.

Operative, a. 1. Acting, active, in action, in operation.

2. Effective, efficient, effectual, efficacious, serviceable.

Operative, n. Laborer, artisan, laboring man, common workman.

Operator, n. Doer, actor, performer, agent, executor.

Operose, a. Laborious, toilsome, hard, onerous, burdensome, difficult, tedious, wearisome, irksome.

Ophite, n. (Min.) Serpentine, green porphyry.

Ophthalmia, n. [L.] Ophthalmy.

Ophthalmy, n. (Med.) Ophthalmia, inflammation of the eye.

Opiate, n. Anodyne, narcotic, sedative.

Opine, v. n. [Obsolete or colloquial.] Think, judge, believe, suppose, conceive, apprehend, fancy, ween, presume, take it, be of opinion, have an opinion.

Opinion, n. 1. Judgment, notion, view, belief, idea, conception, impression, sentiment.

2. Estimate.

Opinionated, a. Conceited, dogmatical, opinionative, stiff or stubborn in opinion.

Opinionative, a. Opinionated.

Opponent, n. Antagonist, adversary, rival, competitor, enemy, foe, adverse party.

Opportune, a. Seasonable, convenient, timely, fit, suitable, favorable, propitious, auspicious, fortunate, lucky, apropos, well-timed, to the purpose.

Opportunely, ad. Seasonably, in the nick of time, all in good time, in the fulness of time.

Opportunity, n. Chance; fit, suitable, or favorable time; good chance, fitting occasion, nick of time.

Oppose, v. a. 1. Resist, withstand, contravene, thwart, oppugn, combat, strive against, set one's face against, make a stand against.

2. Contradict, gainsay, deny.

Opposing, a. Conflicting, counteracting, antagonistic, adverse, opposite, hostile, inimical.

Opposite, a. 1. Facing, over against.

2. Contrary, repugnant, diverse, unlike, incompatible, inconsistent.

3. Adverse, opposed, opposing, antagonistic, hostile, inimical.

Opposition, n. 1. Contrariety, repugnance, diversity, inconsistency.

2. Counteraction, hostility, resistance.

Oppress, v. a. 1. Overburden, crush, overwhelm, overpower, weigh heavily upon, bear hard upon.

2. Persecute, wrong, maltreat, treat cruelly, tyrannize over.

Oppression, n. 1. Hardship, misery, suffering, calamity.

2. Tyranny, severity, cruelty, injustice, persecution.

Oppressive, a. 1. Heavy, overwhelming, overpowering.

2. Tyrannical, cruel, severe, hard, rigorous, inhuman, grinding, galling.

3. Close, uncomfortable.

Oppressor, n. Tyrant.

Opprobrious, a. 1. Reproachful, scurrilous, abusive, vituperative, insolent, condemnatory, damnatory, scandalous, contemptuous, offensive, insulting.

2. Infamous, despised, shameful, dishonorable, disgraceful, disreputable.

Opprobrium, n. Reproach, disgrace, infamy, ignominy, obloquy, odium.

Oppugn, v. a. Assail, attack, combat, resist, oppose, thwart, contravene, withstand, strive against.

Optic, a. Visual.

Optical, a. Visual.

Option, n. Choice, election, preference.

Optional, a. Discretional, elective.

Opulence, n. Wealth, affluence, riches, fortune, independence, easy circumstances, ample means.

Opulent, a. Wealthy, rich, affluent, flush, moneyed, well off.

Oracle, n. 1. Divine communication.

2. (Jewish History.) Sanctuary, Holy of Holies.

3. (Greek History.) Deity or god (from whom divine communications come).

4. Sage, prophet, Solomon, Nestor, wise man, master mind, shining light.