A light scrounging tard is the name given to a chav who goes out and buys cigarettes and yet has no idea you have to light them until they leave the shop and open the packet. They then proceed to ask random members of the public, mainly people they don't like (mostly greebo kids) for a light.
Chav: Yo man, you got a light?
Member of Public: What? You light scrounging tard, you spent about a fiver on a packet of cigarettes and yet didn't spend the 10p needed for a box of matches? Fuck Off!