NARWHAL
narwhal, narwal, narwhale, Monodon monoceros
(noun) small Arctic whale the male having a long spiral ivory tusk
Source: WordNet® 3.1
Etymology
Noun
narwhal (plural narwhals or narwhal)
Monodon monoceros, an Arctic cetacean that grows to about 20 feet (6 meters) long, the male having a single horn-like tusk, a twisted, pointed canine tooth that projects forward.
Synonym: sea unicorn
Source: Wiktionary
Nar"whal, n. Etym: [Sw. or Dan. narvhal; akin to Icel. nahvalr, and
E. whale. the first syllable is perh. from Icel. nar corpse, dead
body, in allusion to the whitish color its skin. See Whale.] [Written
also narwhale.] (Zoöl.)
Definition: 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.
Source: Webster’s Unabridged Dictionary 1913 Edition