marine iguana Syllabification: (ma·rine i·gua·na)Definition of marine iguana noun a large lizard with webbed feet that swims strongly and feeds on marine algae. It is native to the Galapagos Islands and is the only marine lizard. Amblyrhynchus cristatus, family Iguanidae marine iguana in other Oxford dictionaries Definition of marine iguana in the British & World English dictionary