Definition from Wikipedia.org:

Subprime lending, also called B-Paper, near-prime, or second chance lending, is a general term that refers to the practice of making loans to borrowers who do not qualify for the best market interest rates because of their deficient credit history. Subprime lending is risky for both lenders and borrowers due to the combination of high interest rates, poor credit history, and murky financial situations often associated with subprime applicants. A subprime loan is offered at a rate higher than A-paper loans due to the increased risk.