coaster

n. 1. Unuseable CD produced during failed attempt at writing to writeable or
re-writeable CD media. Certainly related to the coaster-like shape of a CD,
and the relative value of these failures. I made a lot of coasters before I
got a good CD. 2. Useless CDs received in the mail from the likes of AOL,
MSN, CI$, Prodigy, ad nauseam. In the U.K., beermat is often used in these
senses.

