genus Amaranthus ge·nu·sa·maranthus uncommon noun 1. large widely distributed genus of chiefly coarse annual herbs SynonymsAmaranthusgenus Amaranthus Related words Broader terms caryophylloid dicot genus Parts Amaranthaceae Part of amaranththorny amaranth WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.