Used to taunt or batter (or batter and then deep-fry) people who use "irregardless" as either a synonym for regardless, or as an antonym for it (that is, as a substitute for the perfectly-understandable "Without regard to".
Adding the prefixes "Not" and "un" cancel each other out in the double-negative, and the "ly" at the end is also character-plaque. Really nice to insert in a business meeting when the denizens are dropping words like "comprise" and using "architect" as a verb that's a $100 synonym for "design".
It's important to maximise the taunt by putting a short ellipses- length or comma-length pause before saying the word, and keeping a neutral expression on your face and looking the victim square in the eyes.
A: We need to re-architect all the syntax that comprise the methods.
B: Well, we need to get our real work done...notunirregardlessly.