1. A multiplayer game in which one person yells, "The floor is lava!" and all other players must comply and find higher ground to get to. Anywhere but the floor is safe and if players stay on the floor, then they are painfully burned to death. The floor becomes safe only when the player that called "lava" recalls that the floor has solidified and is safe to walk upon.
2. An utterance that causes absolute havoc when shouted. The equivalent of yelling "Fire" in a crowded theater, but perfectly legal and much more fun.
"When my friend yelled the floor is lava, I jumped on top of him to save myself and he burned to death."