It's funny you should use that word. I was having a discussion with my folks a few nights ago as to the pronounciation and corresponding meaning of the word. My opinion is that when pronounced twuht as in "what" it means someone who is being silly or lacks common sense (e.g. "Get out of here you twat"), whereas when pronounced as in "that" it's another fine colloquialism from the same basket as pussy, snatch, honeypot, cooter and beaver (e.g. "Hey slag, show us yer twat!").
Thoughts?