When you're walking along and you suddenly let go of every muscle in your body, making it look like you died instantly. Works best next to a pool or on the beach.
Watch me walk along the edge of this pool, I'm gonna instadeath into it.
by GGK78 May 16, 2013
An excessive concentration of something.
Damn this coffee is strong enough to cause instadeath.
by Sara Snider October 11, 2007