The act of performing a snot rocket, but with a friend, usually of the opposite sex. The friend and the shooter connect open mouths, and the friend huffs and puffs a mighty breath through the nasal passages of the shooter, sending snot rockets out both the shooter's nostrils. The friend usually takes the full blast, so it's only recommended for those who have a mucus fetish.
"Did you see Tom and Jillian do the Double Barrel Snot Rocket?" "Yeah d00d! She totally got blasted in the eye!"