Twazzock simply means, simple minded fool, ignoramus or any other words that describe how mentally ignorant or disturbed someone is.
Bob says on a forum with a word filter:
"You are all idiots, any person with a brain would know that the price of that item would obviously be that (prime example on a famous chat applet that uses furniture as a kind of currency which you can buy with currency known as "credits", but you cannot trade them, the furniture has no set price once bought and used.) I traded furniture A for Furniture B (Furniture A being a really expensive item and Furniture B being stupidly cheap and un wanted)"
Now I turn around and say:
"You stupid Twazzock, you have traded for something really cheap with something stupidly expensive"
To show that he is ignorant but thinks he is the bees knees and no one is perfect, basically a sign of being hypocritical.
Instead of swearing at him, you use the word "Twazzock"