The Collaborative International Dictionary of English v.0.48:

Avenue \Av"e*nue\, n. [F. avenue, fr. avenir to come to, L.
   advenire. See Advene.]
   1. A way or opening for entrance into a place; a passage by
      which a place may by reached; a way of approach or of
      exit. "The avenues leading to the city by land."
      --Macaulay.
      [1913 Webster]

            On every side were expanding new avenues of inquiry.
                                                  --Milman.
      [1913 Webster]

   2. The principal walk or approach to a house which is
      withdrawn from the road, especially, such approach
      bordered on each side by trees; any broad passageway thus
      bordered.
      [1913 Webster]

            An avenue of tall elms and branching chestnuts. --W.
                                                  Black.
      [1913 Webster]

   3. A broad street; as, the Fifth Avenue in New York.
      [1913 Webster]

WordNet (r) 3.0 (2006):

avenue
    n 1: a line of approach; "they explored every avenue they could
         think of"; "it promises to open new avenues to
         understanding"
    2: a wide street or thoroughfare [syn: avenue, boulevard]