1. To accidentally bomb or shoot a member of your team, typically in the military.
2. To accidentally shoot your load into your significant other, typically because you were too wasted to time your pull out.
"Holy shit!! .....We just wiped out Bravo company with "Friendly Fire", when we should have targeted 200 yards in front of them where the enemy is positioned!"
"Sorry for the "friendly fire" babe, I'm wasted........"