Noun: A person who represents the lowest
of the low - unemployed, unwashed, but not necessarily
homeless, often invlved in petty crime; the guys you see dregging around downtown as they continue their drunk from the night before while you're on your way to work; reprobates.
"to dreg" describes dreg-like behaviour such as sleeping one off on a park
bench or casing parked cars for easy break-ins.