flea
n.— «A flea, in the parlance of medical students, is an internal medicine resident. And, by way of further explanation—here’s where the pejorative nature comes into play—a flea is “the last thing off a dying dog.”» —“ I dub thee…Sir Flea the Small-Minded!” Aggravated DocSurg (Rocky Mountains) Apr. 29, 2007. (source: Double-Tongued Dictionary)