noun (n)

• a worker employed at a dry-cleaning establishment to remove spots(noun.person)

  source: wordnet30
• a worker employed to apply spots (as markers or identifiers)(noun.person)

  source: wordnet30
• a person employed to keep watch for some anticipated event(noun.person)

  Synonym:
  lookout, lookout man, picket, scout, sentinel, sentry, watch
  

  source: wordnet30
• someone who is the first to observe something(noun.person)

  Synonym:
  discoverer, finder
  

  source: wordnet30
• One who spots.(noun)

  source: webster1913