read-only memory 
(abbreviation ROM)
noun Computing
Memory read at high speed but not capable of being changed by program instructions.The program package includes a read-only memory compact disk (CD ROM) and teacher workbook....
- Another option is to store important programs in read-only memory so that a virus cannot overwrite them.
- Batch inquires are submitted for processing online or on compact disk, read-only memory (CD-ROM) and floppy disks/diskettes.