Definition - What does Coaster mean?
In the IT world, “coaster” is most commonly used to describe non-functional compact discs or DVDs. One of these discs that has been damaged or written to improperly, or ruined while burning, does not present data, and is thus useless. The idea is that one can use it for a coaster for a drink, but not much else.
Techopedia explains Coaster
There are many ways in which a compact disc can become compromised. Sometimes problems like buffer underruns cause functioning problems. Cheap types of hardware devices can turn out high numbers of non-functional disks. Sometimes the improper use of software is a problem as well.
Companies selling high-quality DVD or CD burners sometimes advertise themselves as being “coaster-free,” meaning that every CD is properly burned. Another term that has sprung up around this idea is “coaster toaster,” a term used to describe the inferior burners and hardware devices that turn out non-functional music, video or data discs.