The Collaborative International Dictionary
Dormer \Dor"mer\, or Dormer window \Dor"mer win"dow\, n. [Literally, the window of a sleeping apartment. F. dormir to sleep. See Dormant, a. & n.] (Arch.) A window pierced in a roof, and so set as to be vertical while the roof slopes away from it. Also, the gablet, or houselike structure, in which it is contained.
Wiktionary
n. (alternative form of dormer-window English)
WordNet
n. the window in a gabled extension built to accommodate a window
a gabled extension built out from a sloping roof to accommodate a vertical window [syn: dormer]
Usage examples of "dormer window".
The sound of its motor, barely louder than the ever-present hum of the surf through the dormer window which Tommy had opened, brought the Californian leaping to his feet.
Directly ahead and slightly below him was the dormer window, his entrance to the building that housed Avalon Ltd.
I walked into a small room with a single dormer window, a window seat underneath it, a cot with a white spread, a small desk, a rocking chair.
Amid the smell of glue and hide and shavings they crowded over to the dormer window - that pointed south, and the other side of Montrose was Oregon State University campus, mostly grass and trees.