Coaster

1. Common slang used for either an AOL compact disc or a compact disc that is no longer good, either because of scratches or because of a failure during its creations. The term coaster comes from the coaster commonly used to keep watermarks from being made on tables from drinks.
2. This term is also used to describe recordable discs that have become bad after a burn has failed.

Also see: CD definitions, CD-R, Compact disc