'spotter' definitions:

Definition of 'spotter'

(from WordNet)
noun
A worker employed at a dry-cleaning establishment to remove spots
noun
A worker employed to apply spots (as markers or identifiers)
noun
A person employed to keep watch for some anticipated event [syn: lookout, lookout man, sentinel, sentry, watch, spotter, scout, picket]
noun
Someone who is the first to observe something [syn: finder, discoverer, spotter]

Definition of 'spotter'

From: GCIDE
  • spotter \spot"ter\ (sp[o^]t"t[~e]r), n. One who spots. [1913 Webster]

Synonyms of 'spotter'

From: Moby Thesaurus