[ mon-i-ter ]
See synonyms for: monitormonitoredmonitoring on

  1. (especially formerly) a student appointed to assist in the conduct of a class or school, as to help take attendance or keep order.

  2. a person appointed to supervise students, applicants, etc., taking an examination, chiefly to prevent cheating; proctor.

  1. a person who admonishes, especially with reference to conduct.

  2. something that serves to remind or give warning.

  3. a device or arrangement for observing, detecting, or recording the operation of a machine or system, especially an automatic control system.

  4. an instrument for detecting dangerous gases, radiation, etc.

  5. Radio and Television.

    • a receiving apparatus used in a control room, especially to provide a steady check of the quality of an audio or video transmission.

    • a similar apparatus placed in various parts of a studio so that an audience can watch a recorded portion of a show, the performer can see the various segments of a program, etc.

    • any such receiving apparatus used in a closed-circuit system, as in an operating room.

  6. Computers.

    • the screen component of a computer, especially a free-standing screen.

    • a control program.: Compare operating system.

    • a group of systems used to measure the performance of a computer system.

  7. Nautical.

    • a former U.S. steam-propelled, armored warship of very low freeboard, having one or more turrets and used for coastal defense.

    • (initial capital letter, italics) the first of such warships, used against the Confederate ironclad warship Merrimac at Hampton Roads, Va., in 1862.

  8. a raised construction straddling the ridge of a roof and having windows or louvers for lighting or ventilating a building, as a factory or warehouse.

  9. an articulated mounting for a nozzle, usually mechanically operated, which permits a stream of water to be played in any desired direction, as in firefighting or hydraulic mining.

  10. Also called giant. (in hydraulic mining) a nozzle for dislodging and breaking up placer deposits with a jet of water.

  11. any of various large lizards of the family Varanidae, of Africa, southern Asia, the East Indies, and Australia, fabled to give warning of the presence of crocodiles: several species are endangered.

verb (used with object)
  1. Radio and Television.

    • to listen to (transmitted signals) on a receiving set in order to check the quality of the transmission.

    • to view or listen to (television or radio transmissions) in order to check the quality of the video or audio.

    • to listen to (a radio conversation or channel); keep tuned to.

  2. to observe, record, or detect (an operation or condition) with instruments that have no effect upon the operation or condition.

  1. to oversee, supervise, or regulate: to monitor the administering of a test.

  2. to watch closely for purposes of control, surveillance, etc.; keep track of; check continually: to monitor one's eating habits.

verb (used without object)
  1. to serve as a monitor, detector, supervisor, etc.

Origin of monitor

First recorded in 1540–50; from Latin: “prompter, adviser,” equivalent to monit(us) “reminded” (past participle of monēre) + -or -or

Other words from monitor

  • mon·i·tor·ship, noun
  • self-mon·i·tor·ing, adjective
  • un·mon·i·tored, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use monitor in a sentence

British Dictionary definitions for monitor


/ (ˈmɒnɪtə) /

  1. a person or piece of equipment that warns, checks, controls, or keeps a continuous record of something

  2. education

    • a senior pupil with various supervisory duties

    • a pupil assisting a teacher in classroom organization, etc

  1. a television screen used to display certain kinds of information in a television studio, airport, etc

  2. the unit in a desk computer that contains the screen

    • a loudspeaker used in a recording studio control room to determine quality or balance

    • a loudspeaker used on stage to enable musicians to hear themselves

  3. a device for controlling the direction of a water jet in fire fighting

  4. any large predatory lizard of the genus Varanus and family Varanidae, inhabiting warm regions of Africa, Asia, and Australia: See also Komodo dragon

  5. Also called: giant mining a nozzle for directing a high-pressure jet of water at the material to be excavated

  6. (formerly) a small heavily armoured shallow-draught warship used for coastal assault

  1. to act as a monitor of

  2. to observe or record (the activity or performance) of (an engine or other device)

  1. to check (the technical quality of) (a radio or television broadcast)

Origin of monitor

C16: from Latin, from monēre to advise

Derived forms of monitor

  • monitorial (ˌmɒnɪˈtɔːrɪəl), adjective
  • monitorially, adverb
  • monitorship, noun
  • monitress, fem n

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for monitor


[ mŏnĭ-tər ]

  1. A device that accepts video signals from a computer and displays information on a screen. Monitors generally employ cathode-ray tubes or flat-panel displays to project the image. See Note at pixel.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.