A group of men, usually led by someone named Derek, who meet up at a secret gym to engage in anal sex.
Dan: Looking forward to some Matroom 13 baton strikes this weekend. I wonder when Derek is going to let us know where we're meeting up.
Jason: I know right? Probably near an emergency room this time. He really had it rough with Scott and his crew really tore him up last go around. I had to get him to a doctor the next day. But he loves it so we'll see...