I always called blowing smoke into someonelse mouth a blowback, and a shotgun was when we made a whole at the end of a plastic bottle stuck the joint in it, then burn a carb into the top of the bottle. The bottle fills with smoke (when toking) and when you release the carb and simoutaenouisly(spelling) take out the joint feels like you just shot yourself with a shotgun, a few of 'em gets you soaring..