/ Dictionary / Index J Jacob: Meaning and Definition of Find definitions for: Ja•cob Pronunciation: ( jā'kub for 1, 3 Fr. zha&sylpkôb' for 2), [key] — n. the second son of Isaac, the twin brother of Esau, and father of the 12 patriarchs. Gen. 25:24–34. born 1920, French geneticist: Nobel prize for medicine 1965. a male given name: from a Hebrew word meaning “supplanter.” Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: jacob (Thesaurus) Jacmel Jacob ben Asher Related Content Daily Word Quiz: apogee Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language