mon·i·tor 
(mŏnĭ-tər)
(mŏnĭ-tər)n.
1. One that admonishes, cautions, or reminds, especially with respect to matters of conduct.
2. A pupil who assists a teacher in routine duties.
3.
a. A usually electronic device used to record, regulate, or control a process or system.
b. A video display or speaker used in a production studio to check audio or video quality: The sound engineer detected a hiss on the monitor.
c. Computers A device that accepts video signals from a computer and displays information on a screen; a video display.
4. Computers A program that observes, supervises, or controls the activities of other programs.
5. An articulated device holding a rotating nozzle with which a jet of water is regulated, used in mining and firefighting.
6.
a. A heavily ironclad warship of the 19th century with a low, flat deck and one or more gun turrets.
b. A modern warship designed for coastal bombardment.
7. See monitor lizard.
v. mon·i·tored, mon·i·tor·ing, mon·i·tors
v.tr.
1. To check the quality or content of (an electronic audio or visual signal) by means of a receiver.
2. To check by means of an electronic receiver for significant content, such as military, political, or illegal activity: monitor a suspected criminal's phone conversations.
3. To keep track of systematically with a view to collecting information: monitor the bear population of a national park; monitored the political views of the people.
4. To test or sample, especially on a regular or ongoing basis: monitored the city's drinking water for impurities.
5. To keep close watch over; supervise: monitor an examination.
6. To direct.
v.intr.
To act as a monitor.
[Latin, from monēre, to warn; see men-1 in the Appendix of Indo-European roots.]
moni·tor·ship′ n.