/ Dictionary / Index O old boy: Meaning and Definition of Find definitions for: old boy Pronunciation: (ōld' boi' for 1, 2 ōld' boi&sec for 3 ōld&sec boi' for 4), [key] . an adult male, esp. a Southerner. Cf. a lively elderly man. an alumnus, esp. of a boys' preparatory or public school. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Old Believer old-boyism Related Content Daily Word Quiz: opulent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language