observer

noun

1. One who makes observations, monitors or takes notice.

   “Most impartial observers agreed that Sampras had not served well.”

   “Between 8 and 9 p.m., the recorder at a meteorological station at Harrow, Middlesex, picked up 1,470 lightning flashes within a radius of 10 to 15 miles, and observers at the station described the storm as "probably one of the most spectacular of the century."”

2. One who adheres or follows laws, guidelines, etc.

   “I shall be an observer of the local customs.”

3. A person sent as a representative, to a meeting or other function to monitor but not to participate.

   “The UN sent many observers to the country's first elections.”

   “When the army reached Tsun-i, an enlarged Politburo meeting was called. Teng attended as an observer.”

4. A country or other entity which has limited participation rights within an organization.

   “The Vatican and Palestine have observer status at the UN.”

5. A crew member on an aircraft who makes observations of enemy positions or aircraft.

   “The only crew-member to survive the crash was the Canadian observer.”

6. A sentry etc. manning an observation post.

   “We waited till dusk when the observers' vision was poorest.”

7. Synonym of spotter.