The act saying no, then slapping the knuckle side of your left hand, with the palm of your right hand. It's a sign that really expresses how wrong the other person is in a conversation, or any other way that "no" needs to be heavily expressed. Can also be used instead of saying, "no, never again". Can be expressed as an acromyn over chat, with "sh, no" or just "sh".
Tom: Lets go watch Zoombafoo!
Andrey: No, -slap hands-.
A term from the movie The Waterboy when Bobby Boucher gives or asks for a high five
Also can be used when you give or ask for a high five
*note* when said must be said with a hard lisp
*Guy 1* Hey! SLAP HANDS! *puts up hand for high five*
*Guy 2* SLAP HANDS! *high fives hand*