Monitor  —n. 1 person or device for checking or warning. 2 school pupil with disciplinary or other special duties. 3 a television receiver used in a studio to select or verify the picture being broadcast. B = *visual display unit. 4 person who listens to and reports on foreign broadcasts etc. 5 detector of radioactive contamination. —v. 1 act as a monitor of. 2 maintain regular surveillance over. 3 regulate the strength of (a recorded or transmitted signal). [latin moneo warn]