Is that really what authority means? I always thought it was along the lines of 'famous guy X says Y so Y must be true'. While a dictionary on the other hand is something which I'd really consider authorative i.e. correct when it's about the meaning of words. So a dictionary's reason of existence, it's whole prupose is explaining the meaning of a word, you could say it states the actual facts. Wehereas some famous guy saying something doesn't make it a fact automatically just because he's famous.
It just means the authority is relevant. If you pull out Merriam Webster in an argument about the meaning of the term "racism", you are appealing to authority, which is a logical fallacy. Appealing to authority is a logical shortcut, like any other fallacy, and in a way can be thought of as memoization. Every single logical fallacy has an efficient purpose, but departs from pure logic.
