monitor in WordNet English dictionary

1. someone who gives a warning so that a mistake can be avoided
   admonisher  monitor  reminder 
   
2. any of various large tropical carnivorous lizards of Africa and Asia and Australia; fabled to warn of crocodiles
   monitor  monitor lizard  varan 
   
3. a piece of electronic equipment that keeps track of the operation of a system continuously and warns of trouble
   monitor 
   
4. electronic equipment that is used to check the quality or content of electronic transmissions
   monitor 
   
5. display produced by a device that takes signals and displays them on a television screen or a computer monitor
   monitor  monitoring device 
   
6. someone who supervises (an examination)
   proctor  monitor 
   

1. keep tabs on; keep an eye on; keep under surveillance
   "we are monitoring the air quality"; "the police monitor the suspect's moves"
   monitor  supervise 
   
2. check, track, or observe by means of a receiver
   monitor