from
The Collaborative International Dictionary of English v.0.48
paint gun \paint" gun`\ (p[=a]nt" gun`), n.
1. A device designed to rapidly cover a surface with paint by
ejecting a spray of paint from a reservoir onto the
surface by means of compressed air or other special
mechanism. Also called a {paint sprayer}. Use of a paint
gun is an efficient method to rapidly paint large surface
areas.
[PJC]
2. A device resembling a rifle, designed to shoot a small
quantity of paint at an opponent as part of a game often
conducted at specially-designed indoor locations, or
outdoors. Points are awarded to players who hit their
target; success in hitting one's target is made obvious by
the appearance of a spot of paint on the player who is
hit.
[PJC]