Siamese fighting fish
noun
a labyrinth fish, Betta splendens, that has been bred for centuries to develop brilliant coloration, very long fins, and pugnacity.
Origin of Siamese fighting fish
First recorded in 1930–35
British Dictionary definitions for siamese fighting fish
Siamese fighting fish
noun
a brightly coloured labyrinth fish, Betta splendens, of Thailand and Malaysia, having large sail-like fins: the males are very pugnacious