O1. (n.) O, the fifteenth letter of the English alphabet, derives its form, value, and name from the Greek O, through the Latin. The letter came into the Greek from the Phoenician, which possibly derived it ultimately from the Egyptian. Etymologically, the letter o is most closely related to a, e, and u; as in E. bone, AS. ban; E. stone, AS. Stan; E. broke, AS. brecan to break; E. bore, AS. beran to bear; E. dove; E. toft, tuft; tone, tune; number, F. nombre.
2. (n.) Among the ancients, O was a mark of triple time, from the notion that the ternary, or number 3, is the most perfect of numbers, and properly expressed by a circle, the most perfect figure.
3. (n.) The letter O, or its sound.
4. (n.) Something shaped like the letter O; a circle or oval.
5. (n.) A cipher; zero.
6. (a.) One.
7. (interj.) An exclamation used in calling or directly addressing a person or personified object; also, as an emotional or impassioned exclamation expressing pain, grief, surprise, desire, fear, etc.
Thesaurus Entries
Americanize, Anglicize, O, OK, accept, accord, acculturate, acculturize, acknowledge, acquiesce, acquire, admit everything, admit exceptions, adopt, affiliate, agree, agree provisionally, allow, allow for, assent, assent grudgingly, assimilate, assume, avow, barge in, be admitted, break in, breeze in, brook, burst in, bust in, come barging in, come breezing in, come busting in, come by, come clean, come in, come in for, complete, comprehend, comprise, concede, confer citizenship, confess, consent, consider, consider the circumstances, consider the source, contain, cop a plea, count in, cover, creep in, cross the threshold, crowd in, declare, derive, derive from, discount, dispense, disregard, divulge, drag down, draw, draw from, drop in, edge in, embody, embrace, encircle, enclose, encompass, enter, entertain, envisage, express general agreement, fill, fill in, fill out, gain, gain admittance, get, get in, give an entree, give leave, give permission, give the go-ahead, give the word, go along with, go in, go into, go native, grant, harbor, have, have an entree, have an in, have coming in, hold, hop in, house, immit, include, incorporate, induct, initiate, insert, install, interject, interpose, introduce, intromit, intrude, irrupt, jam in, jump in, leave, let, let in, let on, lift temporarily, lodge, look in, make allowance for, make possible, naturalize, not oppose, number among, obtain, occupy, okay, open up, out with it, own, own up, pack in, permit, plead guilty, pop in, press in, provide for, pull down, push in, put in, receive, reckon among, reckon in, reckon with, recognize, relax, relax the condition, release, reveal, say the word, secure, set aside, set foot in, shelter, slip in, spill, spill it, spit it out, squeeze in, step in, subscribe, suffer, take, take account of, take cognizance of, take in, take into account, take into consideration, take on, take over, take up, tell all, tell the truth, throw open to, thrust in, tolerate, visit, vouchsafe, waive, warrant, wedge in, work in, yield