The Collaborative International Dictionary of English v.0.48:

Listen \Lis"ten\ (l[i^]s"'n), v. i. [imp. & p. p. Listened
   (l[i^]s"'nd); p. pr. & vb. n. Listening.] [OE. listnen,
   listen, lustnen, lusten, AS. hlystan; akin to hlyst hearing,
   OS. hlust, Icel. hlusta to listen, hlust ear, AS. hlosnian to
   wait in suspense, OHG. hlos[=e]n to listen, Gr. kly`ein, and
   E. loud. [root]41. See Loud, and cf. List to listen.]
   1. To give close attention with the purpose of hearing; to
      give ear; to hearken; to attend.
      [1913 Webster]

            When we have occasion to listen, and give a more
            particular attention to some sound, the tympanum is
            drawn to a more than ordinary tension. --Holder.
      [1913 Webster]

   2. To give heed; to yield to advice; to follow admonition; to
      obey.
      [1913 Webster]

            Listen to me, and by me be ruled.     --Tennyson.
      [1913 Webster]

   To listen after, to take an interest in. [Obs.]
      [1913 Webster]

            Soldiers note forts, armories, and magazines;
            scholars listen after libraries, disputations, and
            professors.                           --Fuller.

   Syn: To attend; hearken. See Attend.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

listening \listening\ n.
   the act of hearing attentively.

   Syn: hearing.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

listening
    n 1: the act of hearing attentively; "you can learn a lot by
         just listening"; "they make good music--you should give
         them a hearing" [syn: listening, hearing]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "listening":
   all ears, attention, attentive, audibility, audience, audition,
   aural examination, aural sense, auscultation, bugging, conference,
   eager attention, ear, eavesdropping, electronic surveillance,
   examination by ear, favorable attention, hearing, heeding,
   hushed attention, interview, listening in, open-eared,
   rapt attention, sense of hearing, tryout, wiretapping