We have several dictionaries, and we have no one authority on the English language in the US. Even grammar has no one authority, but just several style manuals, to be used depending on the function of the writing.
Websters is probably the most hated dictionary. I used to have a professor that said that it was easier to use the Sears catalog to find the meaning of words than Websters.
Dictionaries were never meant to govern the language, but to reflect the way words are used in contemporary times. And, words change meaning quickly sometimes. Check out the word "literally" and "thru". The way we use the word, changes it's meaning and sometimes spelling over time.
For example, the antiquated notion that you cannot end a sentence with a preposition, if enforced in some way would have us sounding really dumb, in which it does. In modern conversation we end sentences with prepositions all the time. Otherwise, we sound really dumb.
This is why the entirety of the universe hates an anal retentive grammar nazi.