bellend

Top of the penis, also a British insult. Basically the same as saying "dickhead"

Alex: Hey, did you see how Dan acted at the party last night?

Jamie: Yeah, I couldn't believe it. He was being such a bellend, especially when he started arguing with everyone for no reason.

Alex: I know, right? It was so embarrassing. I hope he realizes how out of line he was.

Jamie: Hopefully, someone talks to him about it. We can't have another night like that.