truck flaps 

labia or pussy lips that are larger and dangle lower than those described as roast beef curtains

As she ran on the nude beach, her truck flaps were clapping in the wind.

truck flaps by rathnite June 30, 2008

Flap Track 

When someone is eating a mans ass in front of a dirt bike exhaust and the receiver revs the motor so their ball bag slaps the ass eaters face/chin.

I'm pretty sure I saw Tommy and Sean flap tracking in the pits last night.

Flap Track by The American Joker May 13, 2022