James has written an interesting post discussing the modern trend of not calling a revolver a pistol. Technically any handgun is a pistol from the early matchlocks to single shot handguns to autoloaders.

I personally use the following terminology:

A revolver: revolver
A single-shot: pistol
A Derringer: Derringer
An Autoloader: pistol (unless it is also a revolver. I would call that an automatic revolver)
A Matchlock: pistol
A fully-automatic handgun: machine pistol (if it was specifically designed to he held like a pistol, otherwise it is a submachine gun)
A handheld cannon: handheld cannon, hand cannon or Handgonne

The futuristic looking Mateba Auto Revolver (from Wikipedia)


Chinese Hand cannon (from Wikipedia)