Option Rom definition in Computer Security terms:
Definition(s): Firmware that is called by the system BIOS. Option ROMs include BIOS firmware on add-on cards (e.g., video card, hard drive controller, network card) as well as modules which extend the capabilities of the system BIOS.
Source(s): NIST SP 800-147
NIST SP 800-147B
reference: CSRC Glossary