/ Dictionary / Index O onanism: Meaning and Definition of Find definitions for: o•nan•ism Pronunciation: (ō'nu-niz"um), [key] — n. withdrawal of the penis in sexual intercourse so that ejaculation takes place outside the vagina; coitus interruptus. masturbation. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: onanism (Thesaurus) on-air Onassis Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language