This pidgin-Latin phrase was General G S Patton's personal motto. He was reputedly asked by a young soldier what advice he could give, to which he replied, "Ne illegitimi carborundum te."
"What does that mean, Sir?"
"Don't let the bastards grind you down."
The "illigitimi" bit speaks for itself. Carborundum is a commercial product, a combination of carbon and silicon used for polishing and grinding.
Therefore, another meaning might be "Don't let the bastards polish you." Take your pick.
I know there are several different suggestions for the correct Latin translation; please don't /msg me with them!