The act of being a total wuss who can't take their booze.
You can spot a 'Cupper' at any party as they are the ones lifting the booze to their lips but failing to actually sup it!!!!
Barbara - "see Brian over there???...... you want to know why he's still standing?????"
Jesus - "Why...... I'm mashed, I've been sick in my hair and can barely see straight and we arrived at the same time?"