Halibut \Hal"i*but\ (?;277), n. [OE. hali holy + but, butte, flounder; akin to D. bot, G. butte; cf. D. heilbot, G. heilbutt. So named as being eaten on holidays. See {Holy}, {Holiday}.] (Zo["o]l.) A large, northern, marine flatfish ({Hippoglossus vulgaris}), of the family {Pleuronectid[ae]}. It often grows very large, weighing more than three hundred pounds. It is an important food fish. [Written also {holibut}.]