A shotty, useless piece of chalk that is not suitable for writing on the blackboard because it is too tiny to grasp.
Prants can also be used as a fun pre-class game called pranting. Object of the game is to make use out of prants, and throw them onto the chalk ledge. Five point for not using the blackboard as a backboard, and three for using it. Each person gets five throws in a round. Highest score at the end of five rounds wins.
"I can't write the Latin homework on the board because all that’s left to write with are god damn prants, open up a new box of chalk, you stingy bastard."
"Dr. G isn't in the class yet, want to engage in a spot of pranting?"