Pronunciation: (ō),[key] —n., —pl.O's or Os; o's or os or oes. 1. the fifteenth letter of the English alphabet, a vowel.
2. any spoken sound represented by the letter O or o, as in box, note, short, or love.
3. something having the shape of an O. 4. a written or printed representation of the letter O or o. 5. a device, as a printer's type, for reproducing the letter O or o.
—interj. 1. (used before a name in direct address, esp. in solemn or poetic language, to lend earnestness to an appeal): Hear, O Israel! 2. (used as an expression of surprise, pain, annoyance, longing, gladness, etc.)
—n. the exclamation “O.”
—Symbol. 1. the fifteenth in order or in a series.
2. the Arabic cipher; zero.
3. (sometimes l.c.) the medieval Roman numeral for 11. Cf. Roman numerals. 4. Physiol.a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group O, A, B, or AB and to receive blood from persons of group O. Cf. ABO system. 5. Chem.oxygen.
6. Logic.See particular negative.
Pronunciation: (u, ō),[key] —prep. 1. an abbreviated form of of, as in o'clock or will-o'-the-wisp. 2. an abbreviated form of on.
a prefix meaning “descendant,” in Irish family names: O'Brien; O'Connor.
Chem. an abridgment of ortho-.
var. of ob- before m: omission.
var. of oo-:oidium.
the typical ending of the first element of compounds of Greek origin (as -i- is, in compounds of Latin origin), used regularly in forming new compounds with elements of Greek origin and often used in English as a connective irrespective of etymology: Franco-Italian; geography; seriocomic; speedometer. Cf. -i-.
1. a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; condo; limo; promo); -o also forms nouns, usually derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (cheapo; pinko; sicko; weirdo; wino).
2. a suffix occurring in colloquial noun or adjective derivatives, usually grammatically isolated, as in address: cheerio; kiddo; neato; righto.
2. (in prescriptions) a pint.