Definition of "monitor"

monitor

/ˈmɒn.ɪ.tə/

noun
plural monitors
1. Someone who watches over something; a person in charge of something or someone.
  Quotations
  And oft, mild friend, to me thou artA monitor, though still;Thou speak'st a lesson to my heart,Beyond the preacher's skill.
  1829, Charles Sprague, To My Cigar
2. A device that detects and informs on the presence, quantity, etc., of something.
3. (computing) A device similar to a television set used as to give a graphical display of the output from a computer.
4. A studio monitor or loudspeaker.
5. (computing) A program for viewing and editing.
6. (Hong Kong, Singapore, archaic in Britain) A student leader in a class.
  Quotations
  So, as she did not like the masters to be prying about the play-ground out of school, she chose from among the biggest and most trustworthy of her pupils five monitors, who had authority over the rest of the Boys, and kept the unruly ones in order.
  1871, Henry William Pullen, The Fight at Dame Europa's School
  But it was not so—at least, not always—for though they fell out among themselves, they united their forces against the common enemy—the monitors!
  1881, Talbot Baines Reed, chapter X, in The Fifth Form at St. Dominic's
  He learned that a monitor should assist the teachers in distributing worksheets, maintaining class discipline, helping classmates in need and so on.
  , Pearl Poon, Class Monitor Election‎, Hong Kong ICAC Comics
7. (nautical) One of a class of relatively small armored warships with only one or two turrets (but often carrying unusually large guns for a warship of its size), usually designed for shore bombardment or riverine warfare rather than open-ocean combat.
8. (archaic) An ironclad.
9. A monitor lizard.
10. (obsolete) One who admonishes; one who warns of faults, informs of duty, or gives advice and instruction by way of reproof or caution.
  Quotations
  You need not be a monitor to your gracious master the king.
  c. 1620, Francis Bacon, letter of advice to Sir George Villiers
  There has been no lack of other monitors — a ticklish haysel, a flooded harvest all through the north […]
  1873, Gardeners Chronicle & New Horticulturist, page 119
11. (engineering) A tool holder, as for a lathe, shaped like a low turret, and capable of being revolved on a vertical pivot so as to bring the several tools successively into position.
12. A monitor nozzle.
verb
third-person singular simple present monitors, present participle monitoring, simple past and past participle monitored
1. (transitive) To watch over; to guard.
  Quotations
  Monitoring refers to keeping a watch over patients to ensure that they are practising what they have learnt about disability prevention correctly.
  1993, H. Srinivasan, Prevention of Disabilities in Patients with Leprosy: A Practical Guide‎, World Health Organization, page 134
  During July 1989-February 1990 ambient SO2, was monitored using a mobile station in the residential-commercial neighborhood of Copacabana.
  1997, Bekir Onursal, Surhid P. Gautam, Vehicular Air Pollution: Experiences from Seven Latin American Urban Centers‎, volumes 23-373, page 239
  A wide-area distributed system such as a Grid requires that a broad range of data be monitored and collected for a variety of tasks such as fault detection and performance monitoring, analysis, prediction and tuning.
  2002, Mark Baker, Garry Smith, GridRM: A Resource Monitoring Architecture for the Grid, in Manish Parashar (editor), Grid Computing - GRID 2002: Third International Workshop, Springer, LNCS 2536, page 268