ONAN.—A son of Judah (Gen_38:4; Gen_46:12, Num_26:19, 1Ch_2:3). After the decease of his elder brother, Er, he was instructed by his father to contract a levirate marriage with Tamar. The device by which he evaded the object of this marriage ‘was evil in the sight of the Lord, and he slew him’ (Gen_38:8-10).