iguanaPronunciation: /ɪˈgwɑːnə/Definition of iguana noun a large arboreal tropical American lizard with a spiny crest along the back and greenish coloration. Genus Iguana, family Iguanidae: two species, in particular the common green iguana (I. iguana) any iguanid lizard. Origin: mid 16th century: from Spanish, from Arawak iwanaiguana in other Oxford dictionaries Definition of iguana in the US English dictionary