1. a resident of a coastal area
2. someone who coasts
3. a covering (plate or mat) that protects the surface of a table (i.e., from the condensation on a cold glass or bottle)
The Collaborative International Dictionary of English v.0.48:
Coaster \Coast"er\, n.
1. A vessel employed in sailing along a coast, or engaged in
the coasting trade.
2. One who sails near the shore.
WordNet (r) 3.0 (2006):
n 1: a resident of a coastal area
2: someone who coasts
3: a covering (plate or mat) that protects the surface of a
table (i.e., from the condensation on a cold glass or bottle)
The Jargon File (version 4.4.7, 29 Dec 2003):
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.