/ Dictionary / Index I incest: Meaning and Definition of Find definitions for: in•cest Pronunciation: (in'sest), [key] — n. sexual intercourse between closely related persons. the crime of sexual intercourse, cohabitation, or marriage between persons within the degrees of consanguinity or affinity wherein marriage is legally forbidden. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: incest (Thesaurus) incessant incestuous Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language