Literally: Don't let the bastards get you down. ie Keep up your struggle against unfair treatment. ("Bastards" in the sense of people who treat you unfairly).
"Are you struggling to obtain your legal rights? Nil Bastardum Carborundum." meaning, literally "don't let the bastards get you down" or "don't give up in your struggle against unfair treatment."

It is a phrase of made-up words designed to sound like a traditional Latin (the language of ancient Rome) motto as used by many schools, universities and similar organizations, also by wealthy high status families or anyone who aspires to such a condition. This type of made-up pseudo- (ie fake) latin is sometimes called cod latinor "pig latin" Compare with J.K. Rowling's motto for Hogwarts school Draco dormiens nunquam titillandus The wrong use of the latin-sounding words is intentionally ironic and carries an implication of a lower class or self- educated person sticking it to "the man", who presumably could afford a classical education.
by T. Regina March 09, 2011
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