pantile

from WordNet (r) 3.0 (2006)

pantile
    n 1: a roofing tile with a S-shape; laid so that curves overlap

from The Collaborative International Dictionary of English v.0.48

Pantile \Pan"tile`\, n. [5th pan + tile.] (Arch.)
   A roofing tile, of peculiar form, having a transverse section
   resembling an elongated S laid on its side (?).
   [1913 Webster]