From WordNet (r) 2.0 (August 2003) [wn]:
shotgun
n : firearm that is a double-barreled smoothbore shoulder weapon
for firing shot at short ranges [syn: scattergun]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Shotgun \Shot"gun`\, n.
A light, smooth-bored gun, often double-barreled, especially
designed for firing small shot at short range, and killing
small game.
[1913 Webster]