Similar to the Wet Willy, a Wet Dippy is the act of administering a Wet Willy while one has a dip in his/her lip. The result is one pissed off individual with brown gooie siliva and possibly bits of yummy tobacco in thier ear. A very humorous site for anyone involved... except of course for the recipient.
Jim: Dude, Andrew just gave Tristan a Wet Dippy!
Bob: Ewww, gross! God it looks like he's got a whole wad in his ear!