RAT ROD?

Rat Rod has become a component of the new Kar Kulture, but what is a RAT ROD? I think the phrase has spread too wide. Lets see if I can subdivide this a bit=
1- Rat Rod - NOT a street rod because a street rod is a finely refined custom usually with a great custom paint job and a defined goal towards perfection. A Rat Rod on the other hand usually a pretty modified drivetrain, but where it strays