Millitary slang for someone scared of confronting the enemy. Like saying coward, only it's not irrational to be scared of red hot tumbling bullets that hit you before you even see the muzzle flash.
"Christ's sake Sarge, don't team me up with Billy, he's Gun Shy! Last time we saw an Iraqi he wet himself, and it was only a woman putting out her washing!"
de Wingy 21 décembre 2005