The Collaborative International Dictionary of English v.0.48:

Imbrication \Im`bri*ca"tion\, n. [Cf. F. imbrication.]
   An overlapping of the edges, like that of tiles or shingles;
   hence, intricacy of structure; also, a pattern or decoration
   representing such a structure.
   [1913 Webster]

WordNet (r) 3.0 (2006):

imbrication
    n 1: covering with a design in which one element covers a part
         of another (as with tiles or shingles) [syn: imbrication,
         overlapping, lapping]