The Collaborative International Dictionary of English v.0.48:

Colt pistol \Colt pistol\ (Firearms)
   A self-loading or semi-automatic pistol with removable
   magazine in the handle holding seven cartridges. The recoil
   extracts and ejects the empty cartridge case, and reloads
   ready for another shot. Called also Browning pistol,
   Colt-Browning pistol, automatic pistol and automatic.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

automatic pistol
    n 1: a pistol that will keep firing until the ammunition is gone
         or the trigger is released [syn: automatic pistol,
         automatic]