Basically someone whos a major idiot, or is delusional and dumb. Acts against logic and thinks hes self-righteous. AKA: Major dumbass.
Good example: Percy from HP and from 5th book
"You stupid prat!"
n. English term, primarily used in United Kingdom. The literal meaning is "bottom" or "rump"; aka backside, buttocks, sacrum, tail end. This lends itself to the slang meaning of "ass," or "clueless person of arrogant stupidity." It is not always directly translatable to American slang. For example, if you used the term "prat hat" in the U.K., you would likely be laughed out of town by the locals.
I can't believe what an overbearing idiot he is. What a prat!
a self-aggrandizing, pompous fuck. Someone who is full of themselves and, almost invariably, stupid as well. With a hint of 'deluded.'
"I'm getting really tired of listening to Vince brag about his conquests. What a prat."
Behaving stupidly, or looking stupid. A British slang word, similar to idiot
Wearing a yellow bowtie made Bob look a right prat.
An English term for "ass", also used to descibe someone as stupid and arrogant.
"No, I lose all bets to the bookies. You can't change fighters at the last minute, so no, I don't have my fight do I, you fucking prat?"
-Alan Ford as "Brick Top" Polford in 'Snatch'
A prat is someone who would actually contribute to Urban Dictionary.
I am a prat.
An overly pretentious person. Someone who is so obviously into themselves that others notice and they fail to realize it.