rebound sex 

the sex that helps someone to recover mentally from failed love affairs.

Example ( The Big Bang Theory S01E03):

Penny: I'm still getting over this break-up with Kurt.
And this thing with Doug would just be rebound sex.
...
It's just -- It's my pattern: I break up, then I find some cute guy

and then it's just 36 meaningless hours of ... well, you know

rebound sex by hans2022 September 29, 2015

Mutual-Rebound-Sex 

The phenomenon in which two acquaintances/friends, both recently single after the dissolution of a long term relationship, become engaged in a purely sexual relationship. This must occur very shortly after the dissolution of said long term relationship.

This phenomenon is quintessentially mutual and void of strategic action and time ordering of events beyond the fact that both of your past relationships ended around the same time. Put bluntly, you both become single and then bam, one night you just start to hook up.

Person 1: It was really strange. Last night I thought I heard Adam leaving Jen's room.

Person 2: Ya that's kinda weird. They both just broke up with their ex's a couple weeks ago

Person 1: I think we're witnessing the MRS phenomenon

Person 2: Huh?

Person 1: Mutual-rebound-sex

Mutual-Rebound-Sex by Elwood Lane January 26, 2013