A word original meaning to have a somewhat large and floppy penis slapped across someones face while they are sleeping. The term has branched out in meanings including to be pwned in a video game or even in real life.
Dude, while Sid was sleeping last night, I completely paddy whacked him. In the morning, he asked me why his face smelled like dick.
Yo, that bitch with the axe just paddy whacked me and killed me in one hit! I completely lost my combo!