A scally is a low life loser who lacks the basic education to string together sentences of more than five words. This prevents them from taking up the only job they are qualified for as they cannot say "Do you want fries with that ?"
To make up for their shortcomings they wear a uniform of fake designer gear and hang around on the streets looking for stuff to rob. The ultimate outfit is anything by LaCoste "Cos its kewl laaa". They normally only own one tracky and their single mothers dont know how to clean it so they are a bit grimy and they stink.
Once a person has succumbed to scallydom there is no saving them and they are doomed to spend the rest of their lives hanging round street corners with other losers drinking cheap cider and 25 lager.
To rebel against their sad lot in life scallies actually create a perverse sense of pride in belonging to the group and attempt to 'out scally, the other members to gain approval.
Is that a dog turd over there or a SCALLY taking a rest?