tuna /ˈtjuː.nə/ noun5 •a big fish of warm seas, with dark red meat, often sold cooked in a can •The edible flesh of the tuna. •The prickly pear, a type of cactus native to Mexico in the genus Opuntia. •The fruit of the cactus. •(slang) Someone who is seen as socially successful despite not being a gang member. formstunas