n. [ Sw. or Dan. narvhal; akin to Icel. nāhvalr, and E. whale. the first syllable is perh. from Icel. nār corpse, dead body, in allusion to the whitish color its skin. See Whale. ] [ Written also narwhale and narwal. ] (Zool.) An arctic cetacean (Monodon monocerous), about twenty feet long. The male usually has one long, twisted, pointed canine tooth, or tusk, projecting forward from the upper jaw like a horn, whence it is called also sea unicorn, unicorn fish, and unicorn whale. Sometimes two horns are developed, side by side. [ 1913 Webster ]