while having sex, just before the climax of ejaculation stick your "head" in or just around the nostril of the girl and jizz in it, until it oozes out like a runny nose.
"oh man i runny nosed my girl last night, and it got all over her face."
when your are recieving some sort of sexual stimulation from a girl, right before you cum, you take the tip of your penis and place it right at her nostril.
"Did you hear? Travis gave the german foreign exchange student a runny nose"