In another place from the one you see it, this would be written "twat".
Sadly, one of two things is currently happening:
1: The administration of the website rigidly enforces censorship by blocking entire posts, or replacing all the letters of certain words with asterisks (*). Fortunately the tw@s have not got to the concept of censoring the other ways of writing that kind of $hit.

2: The writer of the word is far too sensitive and twee to write the word "twat".

There are other examples (such as cvnt, fvck, and $hit) of legitimate alternatives to words that are commonly used to emphasize something, etc.

v. collectively or individually finding someone/something to blame for a problem, as opposed to brainstorming which connotes finding solutions to a problem

n. the act of finding someone/something to blame for a problem

(from a TV ad for HD television)

Another way to write twat. Can be seen on numerous Billboards in The Island of Staunton Island in Grand Theft Auto III

Less offensive way to spell twat, meaning female genitalia.

An @reply tweet to someone on twitter. It can be a noun or verb.

An idiot who tweets too much, esp. a prominent idiot