spotter

Definitions

Construction

  • The person who directs a truck driver into a loading or unloading position.
  • The horizontal framework between the machinery deck of a pile driver and the leads.

Media Studies

  • noun an assistant to a sports commentator who identifies the players in a game

Military

  • noun an officer or NCO who directs artillery fire (usually from an aircraft)

Sports

  • noun a partner who watches a person performing an exercise to check that they are performing it safely and with proper technique
http://www.dictionarycentral.com/definition/spotter.html