The dictionary defines this word as a standing position or position or stand in an argument or debate. So stance where cars are concerned can be defined as the way a car stands/sits on it's wheels.

 

The dictionary defines this word as exageration or very, extremely, insanely etc... The word “hella” is an adjective. It supposedly originated in the San Francisco Bay Area, being a local slang used in place for words mentioned before.

The dictionary defines this word as leveled or even with another surface... The Word "Flush" generally refers to the fitment of wheels and tires with the chassis and fender flares. The closer the wheels are to being flush with the bodywork, the more “hellaflush” that car is.  
This generally requires an obscene amount of camber combined with a stretched tire, which changes the angle of the sidewall of the tire.


All of these photos were taken on the "Edition38 Show&Shine 2013" Overstone Park in Northampton.