Wiktionary
n. A toy gun used to shoot water.
WordNet
n. plaything consisting of a toy pistol that squirts water [syn: water pistol, squirt gun, squirter]
Wikipedia
A water gun (or water pistol, squirt gun, or water blaster) is a type of toy gun designed to shoot water. Similar to water balloons, the primary purpose of the toy is to soak another person in a game such as water warfare.
Historically, water guns were made of metal and used rubber squeeze bulbs to load and propel water through a nozzle
Traditionally, water guns have worked on the same principle as a spray bottle. The body is essentially a container for water and the trigger is attached to a pump which squirts water out of a tiny hole at the muzzle or nozzle. However, many modern water guns employ more complex technologies to provide more power and water output than their predecessors. Modern variations may employ compressed air, rubber chambers, springs, peristaltic pumps, or hydraulic pressure to propel the water. Some even use an electric pump powered by batteries. Some employ a combination of technologies to produce better stream performance. A common term for large high pressure water guns is "water blasters".
For several years in the U.S. and Canada, import regulations and domestic laws have required squirt guns to be made of clear or tinted transparent plastic to make them harder to mistake for actual firearms.