(v.) The act of being non-fatally hit by a drunk driver on St. Patrick's Day.
Jaywalking in front of the Blarney Stone Pub, I was paddywhacked by an oncoming car.
The act of someone grabbing your dick tight, and then slapping the hell out of your balls until you cum. this can be done in several ways, such as the self Paddywhack, and the suspended Paddywhack, where you are suspended uside down and whacked.
that irish girl was crazy last night. my balls are still sore from that Paddywhack.
i gave myself a Paddywhack yesterday because my girlfriend is out of town.