English "illegitimate" in the sense of "bastard", in this case, used as a generic insult. Illegitimis may be intended as an ablative plural, but if carborundum is intended to resemble a gerundive, it is more likely intended as a dative plural, since the gerundive takes a dative of agent. The meaning, in either case, is "by the outlaws/bastards." The second word non is a straightforward negation. The third word, carborundum, is an abrasive used for industrial grinding. It is not a Latin word; instead, it is a genericized trademark derived from the word corundum, a word of Tamil origin. However, it resembles a Latin gerundive, so can be interpreted as a hypothetical "fit to be carborere-ed" or "to be carborere-ed". If (3rd conjugation) were a Latin word meaning "to grind down", Illegitimis non carborundum would be correct Latin for "(It/One) must not be ground down by the outlaws". There are many variants of the phrase, such as Illegitimis non carborundum, Noli illegitimi carborundum and Nil illegitimi carborundum, all of them Dog Latin. Sometimes (as in The Handmaid's Tale), carborundum is prolonged to carborundorum, as if a Latin second declension neuter genitive plural of a noun ending in -um. This is purely jocular and cannot have a grammatical meaning in Latin. See also List of Latin phrases References External links Two alternative explanations Dog Latin words and phrases