Entry 1 sense Webster, 1913 Heinous /(hā"nŭs)/ · Hei·nous · IPA /ˈheɪnəs/ 01 a. Hateful; hatefully bad; flagrant; odious; atrocious; giving great offense; -- applied to deeds or to character. 1. Hateful; hatefully bad; flagrant; odious; atrocious; giving great offense; -- applied to deeds or to character. “It were most heinous and accursed sacrilege.” — Hooker. “How heinous had the fact been, how deserving Contempt!” — Milton. Syn. Monstrous; flagrant; flagitious; atrocious.