The Collaborative International Dictionary of English v.0.48:

Carbine \Car"bine\, n. [F. carbine, OF. calabrin carabineer (cf.
   Ot. calabrina a policeman), fr. OF & Pr. calabre, OF. cable,
   chable, an engine of war used in besieging, fr. LL.
   chadabula, cabulus, a kind of projectile machine, fr. Gr. ? a
   throwing down, fr. ? to throw; ? down + ? to throw. Cf.
   Parable.] (Mil.)
   A short, light musket or rifle, esp. one used by mounted
   soldiers or cavalry.
   [1913 Webster]

WordNet (r) 3.0 (2006):

carbine
    n 1: light automatic rifle