When making sweet love to someone you don't find particularly attractive, neck nuzzling is an effective method to avoid kissing them. By getting stuck into their neck and nuzzling the shit out of it one can avoid looking at the face.
A lesser included offense of cock blocking. Douche Nozzling occurs where one guy is trying to score with a girl and then another guy comes along and tries to get in her pants, i.e., vagina, like that of an actual douche nozzle. The mindset of the douche nozzler is different from that of a cock blocker, as the douche only kind of knows the other guy would have sex with the girl but has not yet made it known that he has made a "claim", so to speak.
That bro is totally douche nozzling his friend's lab partner; he wants to get all up in that vag.