flog the floppies
To smack the shit out of a girl's titties as she is climaxing. Rough tit play.
Friend 1: Man, your girl seems kind of freaky. She's all over me. She says it's okay with you if I fuck her!?

Friend 2: Yeah, dude. Go for it...I just can't keep up with the slut. Just remember to flog the floppies when she cums.