spotter

definition: someone who is the first to observe something
example:
speech part: noun
synonyms: finder
definition: a person employed to keep watch for some anticipated event
example:
speech part: noun
synonyms: picket
definition: a worker employed to apply spots (as markers or identifiers)
example:
speech part: noun
synonyms:
definition: a worker employed at a dry-cleaning establishment to remove spots
example:
speech part: noun
synonyms:

How spotter is being used?