I. noun 1. a small white toothed whale related to the narwhal, living in herds mainly in Arctic coastal waters. Also called white whale.● Delphinapterus leucas, family Monodontidae. 2. a very large sturgeon occurring in the inland seas and associated rivers of central Eurasia.● Huso huso, family Acipenseridae. 3. (also beluga caviar) [ mass noun] — caviar obtained from the beluga sturgeon.
– origin late 16th cent. (in sense 2): from Russian belukha (sense 1), beluga (sense 2), both from belyĭ ‘white’.