Somebody who when discussing an event in the news such as a criminal case, decides that the punishment meted out is not enough.
While mostly ignorant of much of the story, the gnarb-gnasher leaps on the bandwagon to have them not just punished to the full extent of the law, but punished horribly. They get quite creative in saying what should be done to them. It's really scary when you get a lot of them together and they begin to sound like a lynch mob.
The gnarb-gnasher is talking about Tiger. He says, "Tiger Woods cheated on his wife. He should be taken out and horsewhipped and left in the countryside for the birds to pick his brains"
"Oh no," says the other gnarb-gnasher, "let's cut off his narbs and make him eat them. And then roll him down the hill and leave him for the cars to run over his bones!"
Twatman is the drunken guy you seriously need to avoid. He's the one who thinks he's a superhero. He will feel up and slobber over every female within grabbing distance, churning out such winning lines as "You're beautiful, you are. HEY! Did you know that, I said you're beautiful? Cos you are." and "Love, do you wanna come back to my flat and let me fuck you?". These lines are usually delivered whilst Twatman has his face pressed into an unfortunate woman's neck, breathing hotly and rasping his words in a sex killer's voice. Outside, with his mates, Twatman will give them appalling representation by yelling slurred insults at men that were innocently passing by, and inciting a gang style hatred between the two groups, when really, they could have just gone home. Twatman will fight like a retard following a laser pen, will lose and will cry on his knees, bellowing the name of his current or former girlfriend. He will then walk through traffic, dismissing the vehicles as a threat to him and will search out a kebab van. After purchasing the greasy nastiness, he'll wolf it down and puke. He'll tell his mates that he loves them, then get rowdy about it. He'll end his night drenched in sick and gutter filth, plus his own piss, and will be most definitely NOT having sex. He will have ruined everyone's night. These are the powers of Twatman. Bravo.
"Keith turns into Twatman when we go out drinking, lets not invite him, EVER"
"Last night you behaved like a total Twatman, you were really out of order, and you deserve to be horsewhipped, or possibly to die for making that girl cry. I could have ended up fucking her if you hadn't come over and scared her off!"