The Collaborative International Dictionary of English v.0.48:

Archway \Arch"way\, n.
   A way or passage under an arch.
   [1913 Webster]

WordNet (r) 3.0 (2006):

archway
    n 1: a passageway under a curved masonry construction; "they
         built a triumphal arch to memorialize their victory" [syn:
         arch, archway]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "archway":
   French door, apse, arcade, arcature, arch, arched roof, back door,
   barway, bulkhead, camber, carriage entrance, ceilinged roof,
   cellar door, cellarway, concameration, concha, cove, cupola, dome,
   door, doorjamb, doorpost, doorway, front door, gate, gatepost,
   gateway, geodesic dome, hatch, hatchway, igloo, keystone, lintel,
   ogive, porch, portal, porte cochere, postern, propylaeum, pylon,
   scuttle, side door, skewback, span, stile, storm door, threshold,
   tollgate, trap, trap door, turnpike, turnstile, vault, vaulting,
   voussoir