Sex
Or if you want it more formal.. "Love touch". "Dirty dance" is commonly used in parties, when a guy approaches a girl to "dance" but he's actually not trying to be too hideous and in a nice and flirty way, he asks her to hook up.
Guy: We had a dirty dance with my gf  last night~
Guy 2: If only I could have sex with mine too.. She doesn't let me to touch her, since she's on her period.