tuna2Pronunciation: /ˈtjuːnə/Translate tuna | into French | into German | into Italian | into Spanish Definition of tuna noun North American 1the edible fruit of a prickly pear cactus. 2a prickly pear cactus, widely cultivated in Mexico for its edible fruit. Genus Opuntia, family Cactaceae: many species, in particular O. tuna of Central America and the Caribbean Origin: mid 16th century: via Spanish from Tainotuna in other Oxford dictionaries Definition of tuna in the US English dictionary