How good you are feeling about your ability to play beer pong, and win.
"Jason's pongfidence was high after winning 3 rounds. His pongfidence was lost quickly in the semi-finals when he puked on his friends' girlfriend he had been trying to get with. Then he lost the round."
"Bro we gotta get the table, like I've got some mad good pongfidence going, bro."
(Bro to his bro about his pongfident spirit)