Other forms: twats
A twat is either a vagina or a jerk. Either way, this is a very vulgar, obscene word that should be avoided.
You don't hear twat as often as some other four-letter words, but that doesn't mean it isn't offensive. Calling someone a twat is a very dirty way of calling them an idiot, jackass, or bozo. If you refer to a woman's genitals as a twat, that might be even more offensive. So unless you want to get punched in the face or sent to the principal's office, just don't say it.