Source : Webster's Revised Unabridged Dictionary (1913)

Tessellation \Tes`sel*la"tion\, n.
   The act of tessellating; also, the mosaic work so formed.
   --J. Forsyth.

Source : WordNet®

tessellation
     n 1: the careful juxtaposition of shapes in a pattern; "a
          tessellation of hexagons"
     2: the act of adorning with mosaic