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      withdrawn from the road, especially, such approach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]

Moby Thesaurus II by Grady Ward, 1.0:

141 Moby Thesaurus words for "avenue":
   Autobahn, US highway, access, aisle, alley, alleyway, ambulatory,
   aperture, arcade, arterial, arterial highway, arterial street,
   artery, autoroute, autostrada, belt highway, blind alley, blowhole,
   boulevard, bypass, byway, camino real, carriageway, causeway,
   causey, channel, chaussee, chute, circumferential, cloister, close,
   colonnade, communication, conduit, connection, corduroy road,
   corridor, county road, court, covered way, crescent, cul-de-sac,
   dead-end street, debouch, defile, dike, dirt road, door, drag,
   drive, driveway, egress, emunctory, escape, estuary, exhaust, exit,
   expressway, ferry, floodgate, flume, ford, freeway, gallery,
   gravel road, highroad, highway, highways and byways, inlet,
   interchange, intersection, interstate highway, junction, lane,
   local road, loophole, main drag, main road, mews, motorway,
   opening, out, outcome, outfall, outgate, outgo, outlet, overpass,
   parkway, pass, passage, passageway, path, pave, paved road, pike,
   place, plank road, pore, port, portico, primary highway,
   private road, railroad tunnel, right-of-way, ring road, road,
   roadbed, roadway, route nationale, row, royal road, sally port,
   secondary road, sluice, speedway, spiracle, spout, state highway,
   street, superhighway, tap, terrace, thoroughfare, through street,
   thruway, toll road, township road, track, traject, trajet, tunnel,
   turnpike, underpass, vent, ventage, venthole, vomitory, way out,
   weir, wynd