The Collaborative International Dictionary of English v.0.48:

Gangway \Gang"way`\, n. [See Gang, v. i.]
   1. A passage or way into or out of any inclosed place; esp.,
      a temporary way of access formed of planks.
      [1913 Webster]

   2. In the English House of Commons, a narrow aisle across the
      house, below which sit those who do not vote steadly
      either with the government or with the opposition.
      [1913 Webster]

   3. (Naut.) The opening through the bulwarks of a vessel by
      which persons enter or leave it.
      [1913 Webster]

   4. (Naut.) That part of the spar deck of a vessel on each
      side of the booms, from the quarter-deck to the
      forecastle; -- more properly termed the waist. --Totten.
      [1913 Webster]

   Gangway ladder, a ladder rigged on the side of a vessel at
      the gangway.

   To bring to the gangway, to punish (a seaman) by flogging
      him at the gangway.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gangway
    n 1: a temporary passageway of planks (as over mud on a building
         site)
    2: a temporary bridge for getting on and off a vessel at
       dockside [syn: gangplank, gangboard, gangway]
    3: passageway between seating areas as in an auditorium or
       passenger vehicle or between areas of shelves of goods as in
       stores [syn: aisle, gangway]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "gangway":
   Bifrost, access, adit, air lock, approach, bascule bridge,
   bateau bridge, bridge, cantilever bridge, catwalk, corridor,
   drawbridge, entrance, entranceway, entry, entryway,
   floating bridge, flyover, footbridge, gangboard, gangplank, hall,
   in, ingress, inlet, intake, lift bridge, means of access, opening,
   overbridge, overcrossing, overpass, passage, passageway,
   pontoon bridge, rope bridge, span, stepping-stone, stepstone,
   suspension bridge, swing bridge, toll bridge, vestibule, viaduct,
   way, way in