CD-ROM compact disc, read-only memory A compact disc used to store and play back computer data instead of digital audio. CD-ROMs can contain up to 650MB of data (though they often contain a lot less). CD-ROMs have become a favorite medium for installing programs, since they cost only slightly more to manufacture than floppy disks, and most major software applications come on at least five floppies. Don't sound hopelessly out of touch with technology: use the term CD-ROM to refer to the technology or the discs, but not to the hardware you play the discs on. That's a CD-ROM drive. See also: CD-ROM drive