An invigilator is the person who watches an examination so that nobody cheats — walking the rows, checking bags and IDs, calling time, handing out extra paper, collecting scripts. It is a noun for the person, even though the short dictionary line sounds like a verb. British and international-exam English; Americans say proctor. In a Taiwan classroom the everyday title is 監考老師 or 監考人員. The -or ending marks the doer, the way an actor acts. You may also hear exam supervisor, which is plainer and understood everywhere.