When someone shits in another person's ass.
"Normally I don't do Backseat Karls, but $20 is $20"
Two people giving each other oral sex in the back seat of one of their cars
Guy: So we could go get lunch somewhere, where do you want to eat?
Girl: Ooh I know! We could pack a lunch, roll the windows down and have a backseat picnic
Telling someone what or how they should text.
John- Dude you should text her "Fuck You!"
Bob- Quit backseat texting.
A bunch of idiots singing songs terribly as if they were drunk
Today on Backseat and Booze we will sing Sweet home Alabama
While in the back of a car (any even a videogame) posting hentai/r34 to a discord server.
Joakim: Ok im backseating right now.
Geir: Wait, why now?
To love engaging in anal activities
On our first date she told me "backseat are my favourite"
Having intercourse in the back of a car where the female is bent over the back seat
I banged Abbie in the back seat yesterday, gave her a full backseat bender treatment.