The Collaborative International Dictionary
Spray gun
Spray gun \Spray" gun`\ (spr[=a]"g[u^]n`), n. a container for liquid, fitted with a conduit that can be supplied with compressed air, desiged to allowing the contents to be sprayed as an aerosol. Such devices are used to spray paints and various other liquids.
Wiktionary
spray gun
n. paint sprayer, powered by compressed air or other gas, larger than an airbrush.
WordNet
spray gun
n. an applicator resembling a gun for applying liquid substances (as paint) in the form of a spray