The Collaborative International Dictionary of English v.0.48:

Porch \Porch\, n. [F. porche, L. porticus, fr. porta a gate,
   entrance, or passage. See Port a gate, and cf. Portico.]
   1. (Arch.) A covered and inclosed entrance to a building,
      whether taken from the interior, and forming a sort of
      vestibule within the main wall, or projecting without and
      with a separate roof. Sometimes the porch is large enough
      to serve as a covered walk. See also Carriage porch,
      under Carriage, and Loggia.
      [1913 Webster]

            The graceless Helen in the porch I spied
            Of Vesta's temple.                    --Dryden.
      [1913 Webster]

   2. A portico; a covered walk. [Obs.]
      [1913 Webster]

            Repair to Pompey's porch, where you shall find find
            us.                                   --Shak.
      [1913 Webster]

   The Porch, a public portico, or great hall, in Athens,
      where Zeno, the philosopher, taught his disciples; hence,
      sometimes used as equivalent to the school of the Stoics.
      It was called "h poiki`lh stoa`. [See Poicile.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

porch
    n 1: a structure attached to the exterior of a building often
         forming a covered entrance

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "porch":
   Easter sepulcher, French door, ambry, apse, archway, back door,
   baptistery, barway, blindstory, bulkhead, carriage entrance,
   cellar door, cellarway, chancel, choir, cloisters, confessional,
   confessionary, crypt, diaconicon, diaconicum, door, doorjamb,
   doorpost, doorway, front door, gallery, gate, gatepost, gateway,
   hatch, hatchway, lanai, lintel, nave, patio, piazza, portal,
   porte cochere, postern, presbytery, propylaeum, pylon, rood loft,
   rood stair, rood tower, sacrarium, sacristy, scuttle, side door,
   sleeping porch, solarium, stile, stoop, storm door, sun porch,
   threshold, tollgate, transept, trap, trap door, triforium,
   turnpike, turnstile, veranda, vestry