A contemptuous term originally used to describe the poor crowds of 1920s Manhattan. Nowadays can be used to imply that the subject of said insult is scummy and often inspired by questionable goals and motives.
"You ate my sandwhich AND threw the rest of my lunch out? You no-good, son-of-a-bitch trolleydodger!"
"Dude, that guy over there said he'd give me a dollar if I did it."