rose window

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

• noun A large circular window, usually glazed with stained glass, having stone tracery radiating from the center, often with intricate petallike patterns.

from The Century Dictionary.

• noun In architecture, a circular window divided into compartments by mullions or tracery radiating or branching from a center.

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

• noun A generic term applied to a circular window, but especially used for those found in churches of the Gothic architectural style and divided into segments by stone mullions and tracery.

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

• noun circular window filled with tracery