The Collaborative International Dictionary of English v.0.48:

Guilloche \Guil"loche`\, n. [F. guillochis; -- said to be fr.
   Guillot, the inventor of a machine for carving it.] (Arch.)
   1. An ornament in the form of two or more bands or strings
      twisted over each other in a continued series, leaving
      circular openings which are filled with round ornaments.
      [1913 Webster]

   2. In ornamental art, any pattern made by interlacing curved
      lines.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

guilloche
    n 1: an architectural decoration formed by two intersecting wavy
         bands