The Collaborative International Dictionary of English v.0.48:

Discoverer \Dis*cov"er*er\, n.
   1. One who discovers; one who first comes to the knowledge of
      something; one who discovers an unknown country, or a new
      principle, truth, or fact.
      [1913 Webster]

            The discoverers and searchers of the land. --Sir W.
                                                  Raleigh.
      [1913 Webster]

   2. A scout; an explorer. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

discoverer
    n 1: someone who is the first to think of or make something
         [syn: inventor, discoverer, artificer]
    2: someone who is the first to observe something [syn: finder,
       discoverer, spotter]