1. The rapid flashing of your cars
headlights to tell someone to move out of the way.
2. can be used on slow drivers.
3. From the term "F.U
Flash", meaning "Fuck you
Flash"
Driver: This bitch in his Mercury ain't gettin out the way.
Passenger: So bring on the Foo-
Flash!
*
flash flash*
Driver: Next time
don't drive at 40km/h on the freeway!