Source : Webster's Revised Unabridged Dictionary (1913)

Mansard roof \Man"sard roof"\ [So called from its inventor,
   Fran[,c]ois Mansard, or Mansart, a distinguished French
   architect, who died in 1666.] (Arch.)
   A hipped curb roof; that is, a roof having on all sides two
   slopes, the lower one being steeper than the upper one.

Source : WordNet®

mansard roof
     n : a hip roof having two slopes on each side [syn: {mansard}]