1. A practitioner of law who is unethical or immoral. After the accident, I got calls from all sorts of shysters saying I could get rich if I let them sue the company on my behalf. Everyone knows she's a total shyster who'll go to any length to win her case.

2. By extension, someone of a dubious moral or legal standard; a suspected swindler, cheat, or fraud. The shysters said the car was brand new, but it's been having all sorts of problems ever since I bought it.