The Collaborative International Dictionary of English v.0.48:

Musket \Mus"ket\, n. [F. mousquet, It. moschetto, formerly, a
   kind of hawk; cf. OF. mousket, moschet, a kind of hawk
   falcon, F. mouchet, prop., a little fly (the hawk prob. being
   named from its size), fr. L. musca a fly. Cf. Mosquito.]
   [Sometimes written also musquet.]
   1. (Zool.) The male of the sparrow hawk.
      [1913 Webster]

   2. A species of firearm formerly carried by the infantry of
      an army. It was originally fired by means of a match, or
      matchlock, for which several mechanical appliances
      (including the flintlock, and finally the percussion lock)
      were successively substituted. This arm has been
      completely superseded by the rifle, and is now only of
      historical interest.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

musket
    n 1: a muzzle-loading shoulder gun with a long barrel; formerly
         used by infantrymen

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "musket":
   automatic, blowgun, blowpipe, firearm, flamethrower, gat, gun,
   handgun, heater, peashooter, piece, pistol, repeater, revolver,
   rifle, rod, sawed-off shotgun, shooting iron, shotgun, six-gun,
   six-shooter