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.

A phrase to describe someone who is cognitively degenerating. Synonym of "going off the deep end". Can have varying degrees of severity.

Reference to the song "Hey You" by Pink Floyd. The line "and the worms ate into his brain" makes no sense in an otherwise linear and literal narration throughout the lyrics.