The Collaborative International Dictionary of English v.0.48:

Muskellunge \Mus"kel*lunge\, n. [From the Amer. Indian name.]
   (Zool.)
   A large American pike (Esox masquinongy formerly Esox
   nobilior) found in the Great Lakes, and other Northern
   lakes, and in the St. Lawrence River. It is valued as a food
   fish. [Written also maskallonge, maskalonge,
   maskinonge, muskallonge, muskellonge, and
   muskelunjeh.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

muskellunge
    n 1: flesh of very large North American pike; a game fish
    2: large (60 to 80 pounds) sport fish of North America [syn:
       muskellunge, Esox masquinongy]