Software or hardware that is used to scrutinize and to display, record, supervise, control, or verify the operations of a system. Note: Possible uses of monitors are to indicate significant departures from the norm, or to determine levels of utilization of particular functional units. 2. A device used for the real-time temporary display of computer output data. Note: Monitors usually use cathode-ray-tube or liquid-crystal technology. Synonyms CRT, video display terminal, video display unit, visual display unit.