1.) The art of buying a Mcdouble at McDonalds, going to the bathroom, splitting the sandwhich, jizzing on a patty, and going up to someone whacking them in the face with both ends of the McDouble.
2.) When A male gets a casual Handjob in McDonalds from a random female.
Originated In State College, from the Classic S.S.F.
1.) "Oh my God, Leanne just got a McWhack-Attack
from that guy in the panda suit!"
2.) "Every Friday, I got to McDonalds SMASHED at 3 in the Morning and get a McWhack-Attack
from all the prostitutes.