The act of sniffing the hair of your significant other from behind and subsequently shouting the phrase "Doom!" triumphantly, then acting as though nothing happened.
(originating from the Marvel comics character Dr. Doom's many odd images with the scarlet witch, and his tendency to announce his own name loudly).
Person 1: *sneaks up behind girlfriend with the intent of Dooming*
Girlfriend: "... If you Doom me I /will/ slap you."