The Collaborative International Dictionary of English v.0.48:

Alley \Al"ley\, n.; pl. Alleys. [A contraction of alabaster,
   of which it was originally made.]
   A choice taw or marble. --Dickens.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Alley \Al"ley\, n.; pl. Alleys. [OE. aley, alley, OF. al['e]e,
   F. all['e]e, a going, passage, fr. OE. aler, F. aller, to go;
   of uncertain origin: cf. Prov. anar, It. andare, Sp. andar.]
   1. A narrow passage; especially a walk or passage in a garden
      or park, bordered by rows of trees or bushes; a bordered
      way.
      [1913 Webster]

            I know each lane and every alley green. --Milton.
      [1913 Webster]

   2. A narrow passage or way in a city, as distinct from a
      public street. --Gay.
      [1913 Webster]

   3. A passageway between rows of pews in a church.
      [1913 Webster]

   4. (Persp.) Any passage having the entrance represented as
      wider than the exit, so as to give the appearance of
      length.
      [1913 Webster]

   5. The space between two rows of compositors' stands in a
      printing office.
      [1913 Webster]

WordNet (r) 3.0 (2006):

alley
    n 1: a narrow street with walls on both sides [syn: alley,
         alleyway, back street]
    2: a lane down which a bowling ball is rolled toward pins [syn:
       bowling alley, alley, skittle alley]

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "alley":
   Autobahn, US highway, access, aisle, alleyway, ambulatory,
   aperture, arcade, arterial, arterial highway, arterial street,
   artery, autoroute, autostrada, avenue, belt highway, blind alley,
   boulevard, bypass, byway, camino real, carriageway, causeway,
   causey, channel, chaussee, circumferential, cloister, close,
   colonnade, communication, conduit, connection, corduroy road,
   corridor, county road, court, covered way, crescent, cul-de-sac,
   dead-end street, defile, dike, dirt road, drive, driveway, exit,
   expressway, ferry, ford, freeway, gallery, gravel road, highroad,
   highway, highways and byways, inlet, interchange, intersection,
   interstate highway, junction, lane, local road, main drag,
   main road, mews, motorway, opening, outlet, overpass, parkway,
   pass, passage, passageway, pave, paved road, pike, place,
   plank road, portico, primary highway, private road,
   railroad tunnel, right-of-way, ring road, road, roadbed, roadway,
   route nationale, row, royal road, secondary road, speedway,
   state highway, street, superhighway, terrace, thoroughfare,
   through street, thruway, toll road, township road, traject, trajet,
   tunnel, turnpike, underpass, wynd