A shout of joy, written down. It comes from the Internet and from gaming, and it means something like "yes!" or "we did it!" — the sound a person makes when something good just happened to them. You see it alone as a whole message ("Woot!"), or in front of the good news ("Woot, I passed!"). People often stretch it — "woooot" — or write "w00t" with two zeros, which is the older gamer spelling; both are the same word. It is very informal. It belongs in a chat message, a comment, a text to a friend. It does not belong in an email to your boss or in any piece of school writing, and an older person who does not use the Internet much may not know it at all. It is also going a little out of fashion — it was everywhere around 2005-2010, and younger people now are more likely to type "lets gooo" or just a row of emoji. That does not make it wrong; it makes it sound slightly like an older Internet person, the way an old slang word sounds in any language. One more thing worth knowing: because it is only a noise, it carries no information. "Woot" tells your reader you are happy but not why, so it usually arrives next to the news rather than instead of it.