Translation for the layperson: it is basically a clean version of "fuck off," sans profanity. It is unlikely that one would say this to another without a justified/specific reason to be pissed at them. Basically, one is ordering the other to not talk to them, or even come near them. Preferably get out of their sight altogether.
Short-hand for the word floccinaucinihilipilification, meaning the estimation of something as valueless (encountered mainly as an example of one of the longest words in the English language).