A
small firearm kept in your
sock, or on a
chain around your
neck, or in a special
holster between your
belt and your
pants, for those times when you've been disarmed, and there's a
bad guy about to seriously ruin your day, and you really really wish you had a gun.
Commonly available in .17, .22, .25, and .27 caliber.
See also:
Derringer