Mān'sard-rōof, n.

noun

n. [So called from its inventor, Fr. Mansard, a French architect, who died in 1666.] (Arch.) A kind of roof formed with an upper and under set of rafters, the upper set more inclined to the horizon than the under set;— called also curb-roof. Weale.

A labeled diagram of a mansard roof showing its rafters, collar beam, and tie beam.
Mansard-roof.