co-lo = C = coaster toaster

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.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.