I keep hearing the term "defuel Levels" with the tuners, what does this mean?

 

Maybe someone else has a better explanation (I hope).

Defueling is when certain set parameters are exceeded and the computer/program cuts fuel back. Fuel is what controls many things in a diesel and is related to heat and pressure. Usually these programmers, and the use of the trucks, are pushing limits and defueling is a safety release so to speak to keep from damaging things when pushing hard.