Face sex. Like making out but more forceful. Prolonged snogging.
A really really really long makeout session.
Dude1: Hey, we ask Trevor if he wants to come with us!
Dude2: No way. I went in there an hour ago and him and this chick were having snex.
Dude1: Ahh gross. I heard she's a freaky kisser.
Dude2: She must be. She had him in a headlock.