monitor

monitor is a Noun

Definition:

[1] One who admonishes; one who warns of faults, informs of duty, or gives advice and instruction by way of reproof or caution. You need not be a monitor to the king. Bacon.

[2] Hence, specifically, a pupil selected to look to the school in the absence of the instructor, to notice the absence or faults of the scholars, or to instruct a division or class.

[3] Any large Old World lizard of the genus Varanus; esp., the Egyptian species (V. Niloticus), which is useful because it devours the eggs and young of the crocodile. It is sometimes five or six feet long.

[4] An ironclad war vessel, very low in the water, and having one or more heavily-armored revolving turrets, carrying heavy guns.

[5] 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 successively the several tools in holds into proper position for cutting. Monitor top, the raised central portion, or clearstory, of a car roof, having low windows along its sides.