Source : Webster's Revised Unabridged Dictionary (1913)

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 (?).

Source : WordNet®

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