Riding Bronco 

Riding in the storage area of an SUV, van or station wagon without any actual seat or seatbelt.

If you didn't call shotgun, window or bitch you'll be riding bronco, so I hope you brought a pillow for your ass because that shit is uncomfortable.

Riding Bronco by LennySands March 6, 2011

Riding Broncho 

When a man is getting a girl up the ass, and before she comes you whisper, "This is how your sister liked it." This causes her to try to get up, as you hold on and keep going.

Jack gave Jill the old Riding Broncho!

Riding Broncho by Patrick McSweeney September 5, 2003