Ball your fist up, and lightly "bop" the bottom, or soft part of it, on someone's forehead after saying the words, "Ball up!" it's a verbal and physical response to someone who fails/messes up/is just plain wrong/ or does something stupid when trying to make themselves look cool or smart. Some people even say, "bink!" while simultaneously applying the forehead bop.
"Boise State deserves to play for a National Championship."
"I tried to get that chicks number, but she told me she'd rather swallow gasoline than continue the conversation..."