1) To beat the holy hell out of someone
2) To anihilate a girl sexually
1)That dude has been starting shit with my friend. Let's smash attack him!
2)You know that hot chick from Paramore? I'd smash attack her.
One of the best ways to hug someone. Similar to a glomp. Generally, you run to someone and hug them. Some people may yell 'smash attack.'
Sally: Today I smash attacked Julie after school and it was really funny.
Anne: Haha, I saw that.