The Collaborative International Dictionary of English v.0.48:

Imbricate \Im"bri*cate\, Imbricated \Im"bri*ca`ted\, a. [L.
   imbricatus, p. p. of imbricare to cover with tiles, to form
   like a gutter tile, fr. imbrex, -icis, a hollow tile, gutter
   tile, fr. imber rain.]
   1. Bent and hollowed like a roof or gutter tile.
      [1913 Webster]

   2. Lying over each other in regular order, so as to "break
      joints," like tiles or shingles on a roof, the scales on
      the leaf buds of plants and the cups of some acorns, or
      the scales of fishes; overlapping each other at the
      margins, as leaves in [ae]stivation.
      [1913 Webster]

   3. In decorative art: Having scales lapping one over the
      other, or a representation of such scales; as, an
      imbricated surface; an imbricated pattern.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Imbricate \Im"bri*cate\, v. t.
   To lay in order, one lapping over another, so as to form an
   imbricated surface.
   [1913 Webster]

WordNet (r) 3.0 (2006):

imbricate
    adj 1: used especially of leaves or bracts; overlapping or
           layered as scales or shingles [syn: imbricate,
           imbricated]
    v 1: place so as to overlap; "imbricate the roof tiles"
    2: overlap; "The roof tiles imbricate"