When someone is holding an item (usually a drink) and you slap their hand(s) in an attempt to make the person drop the item. This is accompanied by yelling "Grip check!".
"Grip check bitch! *POW*"
by Black Ass Todd August 10, 2013
A simple test of strength that sometimes occurs when two alpha males shake eachother's hands for the first time. The process includes squeezing as hard as you can until one person gives up.
Chet hasn't met Brad yet? Get ready for a grip check!
by Teh_Guy November 12, 2010