Ja·cob (j??k?b) In the Bible, the son of Isaac and grandson of Abraham. His 12 sons became the progenitors of the 12 tribes of Israel.[Late Latin Iac?bus, from Greek Iak?b, from Hebrew ya’?q?b, (God) has protected; see ?qb in Semitic roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Jacob (?d?e?k?b) n1. (Bible) Old Testament the son of Isaac, twin brother of Esau, and father of the twelve patriarchs of Israel2. (Animals) Also called: Jacob sheep any of an ancient breed of sheep having a fleece with dark brown patches and two or four horns[sense 2 in allusion to Genesis 30:40]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Ja?cob (?d?e? k?b) n. a son of Isaac and Rebekah, younger twin of Esau, and father of the 12 patriarchs. Gen. 24:24?34. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.