When two gay lovers face each other whilst holding their dicks in an angry manner. They both then turn (back to back) and walk roughly ten paces. After pacing one or the other then turns, runs after his partner and penetrates him anally before the other can turn around. In this scenario, typically the "top" is considered the winner.
This act is often used to settle spats between lovers.
"I was so pissed off at Bruce last night. I found out that he let Toby suck his dick in the walk-in freezer at work. I challenged him to Pistols at Dawn and he won! that bitch! He didn't even lube up before hand! It's okay though, I didn't take a shit all day so he had a surprise waiting for him when he pulled out.
I'm gonna go down to the Blue oyster bar tonight if you want to join me."