brake test

Speeding in front of another driver and then immediately applying the brake, causing this driver to have to stop quickly as well - testing the brakes on their car while evening the score. Usually used as a retaliatory measure against a stupid driver who has pissed you off. Works well on hypermilers.
As a side note - Brake testing should under no circumstances be performed while your wife/girlfriend is in the car. They don't appreciate the need for immediate retribution.