dive on the hand grenade 

To seduce an ugly girl so that your buddy can score with her attractive friend. This expression comes from the act of war-time bravery where a soldier would sacrifice himself to save his buddies. If you're out on the prowl with a mate and he is making progress with a fox, it is his friend's duty to chat up and seduce the pretty girl's ugly friend so that your buddy is free to leave with the hotty.

Dude, tonight it's your turn to dive on the hand grenade.

dive on the hand grenade by Bradboy January 10, 2007