Used to mock someone or something behind their back. Pronounced in a half-whispered, warbling voice and lasts for roughly 2 seconds. Usually used in response to a story about someones dim-witted antics. Sometimes followed by 'Imagine if he died!' or various insults. It is also often used by pretentious indie kids who think that bands who make money are highly uncool. Paaah is never said to the object of mockery's face, only behind their back.
John: "Hey did you here what Alfstaz did? He ate a candle because he thought it was made of honey!"
Jim: "Paaah imagine if he died!"
John: "Look at James! He's wearing an Arctic Monkeys T-Shirt!"
Jim: "Didn't they have the highest selling British debut album of all time and have tow consecutive number one singles?"
Jim: "Paaah what a fucking twat!"