Tweet" became an official word in the Oxford English Dictionary about two

The word "tweet," meaning a message posted on the social media site
Twitter, was first recognized as an official word by Merriam-Webster in
2011, and in June 2013, the word was added to the Oxford English Dictionary
(OED). The addition of "tweet" occurred about two years after OED had made
an official word of "retweet," which means to forward another person’s
tweet. Each dictionary has its own rules about the criteria a word must
meet before being added, but exceptions might be made for words that gain
widespread usage especially quickly. For example, OED generally requires a
word to have been in use for 10 years before being added, but "tweet" was
added about six years after it was first used in this context.