Icebox is an adjective used to describe something especially chill, dank, or cool. A group of guys chilling, having a great time, would characterize their adventures and exploits as icebox. If things take a turn for the worse, then that situation is no longer icebox and has become freezerburnt.
Dude 1: "Yo is everything okay?"
Dude 2: "Chill dude, its all icebox."