transept

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

• noun The transverse part of a cruciform church, crossing the nave at right angles.
• noun Either of the two lateral arms of such a part.

from The Century Dictionary.

• noun In architecture, the transverse arm of a cruciform church; technically, one of the two subdivisions of this arm, one on each side of the body of the church, generally described as the north or the south transept.

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

• noun (Arch.) The transversal part of a church, which crosses at right angles to the greatest length, and between the nave and choir. In the basilicas, this had often no projection at its two ends. In Gothic churches these project these project greatly, and should be called the arms of the transept. It is common, however, to speak of the arms themselves as the transepts.

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

• noun architecture The transversal part of a church, which crosses at right angles to the greatest length, and between the nave and choir. In the basilicas, this had often no projection at its two ends. In Gothic churches these project greatly, and should be called the arms of the transept. It is common, however, to speak of the arms themselves as the transepts.

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

• noun structure forming the transverse part of a cruciform church; crosses the nave at right angles