1. Any of several prickly pears; especially, a treelike pear of tropical America with an edible fruit or the fruit itself: "When Mary was in her biology class the other day, the class read about tuna, which is also a kind of cactus, not only a fish!"

"Mary also found out that the fruit of this cactus; especially, that of the Opuntia tuna of Jamaica has spiny flat connections between the flat leaves, its fruit is oval and red, and it is used primarily as food for livestock."

2. Etymology: from American Spanish and previously from Taino.