sleepwalk sex
When someone has sex with somebody else while sleepwalking, and usually doesn't even know that they did it.
Dude, John slept over my house last night, and he gave it to me up the ass at 1 a.m. while muttering something about trees!
Ahh, so he had sleepwalk sex with you?
Yup.
Ahh, so he had sleepwalk sex with you?
Yup.