A high-volume fart that is so powerful it propels your junk forward, painfully slapping the parts against your belly or thigh.
To perform a ball blaster, put on loose-fitting boxers (or nothing at all), get in a reclining position, spread your legs, brace for the pain, and let it rip. Hard.
A blister that forms on a males testicles after sitting in his dingey tighty whiteys and creating lumps and sores from the caked and moistened fecal matter ther is suck on them.
That homeless dude has been sitting in his shit forever. I bet you he has enormous dingey ball blisters!