A group of men talking in a circle, triangle, square, or any kind of closed or almost shape. Usually happens at large events over manly subjects on accident. Usually realized when the first female approaches.
Men: "Dude, I totally tapped tha.."
Girl: "Hey guys, whats up?"
Dude 1: "TITS!"
Dude 2: "Oh shit! Sorry miss, but this is the MAN CIRCLE."