The act of going up onto a roof with a cinder block, facing away from the edge - then picking up the cinder block with both hands and flinging it backwards over
your head in the same way a catapult would, tossing the cinder block onto
the street below. The perceived purpose of the Baltimore Trebuchet is to hit the cars parked in
the street below.
"Yo I heard Joey got
arrested last night, what
happened?"
"Ah, he got super drunk and decided to start a game of Baltimore Trebuchet."
"Damn, I knew that guy was a dumbass."