Your use of the word "official" is the difficult part here. Unlike French or Spanish where there is at least ostensibly an academy which makes 'official' decisions about vocabulary , no such entity exists for English. I'd agree with duguup that the Oxford English Dictionary (OED) is generally viewed as the definitive reference, to the extent that such a thing exists. However, keep in mind that the OED is, in its own words "a dictionary on historical principles". That is, it seeks to include any word that has ever been part of the English language, and you will find many words in it which have passed out of common usage.

Every year, Oxford English Dictionary and Merriam Webster English Dictionary decide which words to add to their publications. The way they do this is by monitoring how often a word gets used in newspapers, magazines, etc. After a word has spread far enough, it is added to the next edition of their dictionary.