The Collaborative International Dictionary of English v.0.48:

Flintlock \Flint"lock`\, n.
   1. A lock for a gun or pistol, having a flint fixed in the
      hammer, which on striking the steel ignites the priming.
      [1913 Webster]

   2. A hand firearm fitted with a flintlock; esp., the
      old-fashioned musket of European and other armies.
      [1913 Webster]

WordNet (r) 3.0 (2006):

flintlock
    n 1: a muzzle loader that had a flintlock type of gunlock [syn:
         flintlock, firelock]
    2: an obsolete gunlock that has flint embedded in the hammer;
       the flint makes a spark that ignites the charge