a. (Zool.) Of or pertaining to the Helianthoidea. [ 1913 Webster ]
‖n. pl. [ NL., fr. L. helianthes sunflower + -oid. ] (Zool.) An order of Anthozoa; the Actinaria. [ 1913 Webster ]
n. any plant of the genus Helianthus having large flower heads with dark disk florets and showy yellow rays. Syn. -- sunflower. [ WordNet 1.5 ]