A person riding between the driver and passenger in a pickup truck. Generally an uncomfortable position in the cab, hence the name.

Sitting in-between the driver and the passenger in a vehicle or sitting behind the driver on a motorcycle.

The person forced to sit in the middle of the back seat or in between the two front seats in a two seater in a car. Usually the smallest person or only female in the group will have to ride 'bitch', so that the guys don't touch each other (irrational male homophobia)

the passenger (usually female) on the back of a motorcycle.

is when your friend calls shot gun and your stuck sitting in the middle like a bitch. there for you are riding bitch because you are the bitch.

Often in the back seat of a car, Sitting in the middle of 2 other people. It's rally annoying.