The Collaborative International Dictionary of English v.0.48:

Listener \Lis"ten*er\ (l[i^]s"'n*[~e]r), n.
   One who listens; a hearkener.
   [1913 Webster]

WordNet (r) 3.0 (2006):

listener
    n 1: someone who listens attentively [syn: hearer, listener,
         auditor, attender]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "listener":
   accepter, acquirer, addressee, audience, audient, audiophile,
   auditor, beholder, consignee, eavesdropper, getter, hearer,
   hearkener, hi-fi fan, holder, listenership, looker, obtainer,
   overhearer, payee, procurer, receiver, recipient, snoop, spectator,
   taker, trustee, viewer