Rub Bunnies

Situational lesbianism. When two women engage in a sexual act, but only because it also involves a male. Often facilitated by the use of drugs and/or alcohol.
Also:

Rubbing bunnies (present tense)
Rubbed bunnies (past tense)

Yes, Tim, let's do ecstasy and go back to your apartment. Kim and I are new friends, so this will give us a chance to rub bunnies.

Bunny Rub

A sweeter way to say Titty Fucking

Sarah gave me a bunny rub last night. It felt so good, I came all over her tits after.