Butt sex. When a guy sticks his penis into a lady's ass hole. The penis usually ends up covered in poopies and generally quite dirty. this is where the expression comes from. Cuz usually if you go 4 wheeling in the backcountry, your car will end up covered in mud. Mud resembles poop and the car is a metaphore for your penis.
Female Infidel: OMG! Timmy was so horny last night but i was on my period. I let him go four-wheelin in the backcountry. It smelt like poops and now i cant control my sphincter so i wear a diaper.
Infidel: I went four-wheelin in the back country yesterday. Ass hole is the second vagina.
A repulsive sexual maneuver when you are having sex with a girl with a warbling double chin. You jab your dick in her mouth, making her chin vibrate as she is making turkey sounds. Just before ejaculation you pull out and turn her around, going for the dirt road while she is on all four.
That Tom is such a quitter, I really wanted to get a hold of him but he was out four wheeling with the turkey lady all weekend.