freeway flirt 

A driver or passenger that constantly attempts to catch another driver's attention on the road (or the passengers in the car, usually if their windows are open), usually by making faces or smiling.

Is also a common hobby for bored people in the backseat.

Look at Sarah making faces at that guy in the red Honda. She's such a freeway flirt!

freeway flirt by Billie Jean Lee August 25, 2007

freeway flirting 

When two people check each other out and flirt from car to car while driving. Nods and suggestive gestures are common.

He nodded at me and I tossed my hair and stuck out my chest. It was total freeway flirting.

freeway flirting by shoe_whore November 19, 2007