Review of vWorker formerly known as RentACoder. I have a soft corner towards RentACoder as it was the first site where I won the first few of my freelancing work.
Oxford dictionary defines freelance as - Self-employed and hired to work for different companies on particular assignments.
Any individual working for multiple clients or companies without being permanently employed by any one of them is a freelancer. The working freelancers are commonly termed as "doing freelancing" or "Freelancing"