Definition of ROM
Read-only memory (ROM) refers to a storage technology that allows you to write data only once. After the data has been written, you can read it an unlimited number of times. Contrast this with random-access memory (RAM) that allows you to read and write data as many times as needed.
Originally, the term ROM referred to memory chips. However, with the creation of other stored devices, the term is being used more widely. In particular, CD-ROM is used to distinguish CDs that can only be read and not written too.