A situation in which a heterosexual male human being is having anal sex with a female human being in the doggystyle position and a 2nd male enters the room and inserts his penis into the other male's anus from behind. The male in the middle is perplexed as to whether he should continue his anal sex with the woman while he gets it from behind or if he should just stop altogether.
Male 1: "I hooked up with the hottest girl at the club last night and everything was going fine until she surprised me with the dirt rod."
Male 2: "Oh man! So did you stop or continue?"
Male 1: "I finished and got the hell out of there!"
That's a certified dirt rod