mansard roof

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A roof having a double slope on all sides, with the lower slope much steeper than the upper.

from The Century Dictionary.

• noun See roof.

from the GNU version of the Collaborative International Dictionary of English.

• (Arch.) A hipped curb roof; that is, a roof having on all sides two slopes, the lower one being steeper than the upper one.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A roof having two slopes on each side, the lower one having a steeper pitch than the upper; this increases the volume of the enclosed space.
• noun A steeper roof that terminates into a flat roof at its high point.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a hip roof having two slopes on each side