The term not bitch is actually a secondary to shotgun and cannot be used to call the front seat but to garantee you don't get the worst seat (usually the middle seat).

a spanish word meaning the flipflop
used by latin moms to beat their child's ass

When the position of shotgun has already been filled the rest of the passengers call out "Not bitch" in order to not have to sit in the middle seat (aka bitch seat)

The worst seat in a car besides bitch (back middle). Whoever sits in it must get out or slide over to the middle if a 5th person gets in the car.

intj. This phrase is used to reserve a seat in a vehicle which is not bitch.

The first person to call not bitch gets the front seat; people after that get distributed around the car. If you chronically forget to call not bitch, you will always sit in the middle seat.

The rules for calling not bitch are the same as those for shotgun.