An Attitude Adjustment Tool. Primary training tool of the Extreme Programming Master. Related to the Two By Four commonly used to train mules.
Snoopy said that this tends to give one a distorted view of the press!
Not sure if it's common usage, but I've seen the verb "fwap" used to describe use of this particular tool.
Different from a Clue Stick in that it does not necessarily bring enlightenment.
See: Zen Slap, Brutal Sarcasm, Clue By Four, Clue Stick
See original on c2.com 