[1] : The Collaborative International Dictionary of English v.0.48

arch \arch\ aumrch, n. f. arche, fr. ll. arca, for arcus.
   see arc.
   1. geom. any part of a curved line.
      1913 webster

   2. arch.
      a usually a curved member made up of separate
          wedge-shaped solids, with the joints between them
          disposed in the direction of the radii of the curve;
          used to support the wall or other weight above an
          opening. in this sense arches are segmental, round i.
          e., semicircular, or pointed.
      b a flat arch is a member constructed of stones cut into
          wedges or other shapes so as to support each other
          without rising in a curve.
          1913 webster

   note: scientifically considered, the arch is a means of
         spanning an opening by resolving vertical pressure into
         horizontal or diagonal thrust.
         1913 webster

   3. any place covered by an arch; an archway; as, to pass into
      the arch of a bridge.
      1913 webster

   4. any curvature in the form of an arch; as, the arch of the
      aorta. "colors of the showery arch." --milton.
      1913 webster

   triumphal arch, a monumental structure resembling an arched
      gateway, with one or more passages, erected to commemorate
      a triumph.
      1913 webster
see also:
arc triumphal arch 

[2] : WordNet (r) 2.0

triumphal arch
     n : a monumental archway; usually they are built to commemorate
         some notable victory

Arch >> A Words
Arch, definition of term: Arch
arch_pag1.html

Aortic Arch >> A Words
Aortic Arch, definition of term: Aortic Arch
aortic+arch_pag1.html