beluga

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small toothed whale (Delphinapterus leucas) chiefly of the Arctic Ocean, having a bulbous forehead and a white body when full-grown.
• noun A large white anadromous sturgeon (Huso huso) of the Black and Caspian Seas, valued for its roe.
• noun Caviar made from the roe of this fish, having large grayish grains.

from The Century Dictionary.

• noun The large white sturgeon, Acipenser huso, from the roe of which, sometimes weighing 800 pounds, caviar or botargo is prepared.
• noun [capitalized] [NL.] A generic name of the white whales: a synonym of Delphinapterus.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A cetacean allied to the dolphins.
• noun the sturgeon (Huso huso) native to the Black Sea and Caspian Sea; -- also called hausen. It is valued for its roe, sold as caviar, and is also used for production of isinglass. See also sturgeon.
• noun the caviar obtained from the beluga{2}; -- also called beluga caviar. The caviar of the beluga is considered the finest sort, larger and of a taste superior to that obtained from other sturgeon. See also sturgeon and caviar.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A cetacean, Delphinapterus leucas, found in the Arctic Ocean.
• noun A fish, Huso huso, found in the Caspian Sea and the Black Sea, that is a source of caviar

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun valuable source of caviar and isinglass; found in Black and Caspian seas
• noun small northern whale that is white when adult