Mōn'i-tor, n.

n. [Lat., It. monitore, Sp. monitor, Fr. moniteur.] 1. One who monishes or 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 scholars in the absence of an instructor, or to notice the absence or faults of the scholars, or to instruct a division or class.
3. (Zoöl.) One of a family of lizards inhabiting the warmer parts of the eastern continent, so called from being supposed to give warning of the vicinity of crocodiles.