Definition of clerestory
noun (plural clerestories)
the upper part of the nave, choir, and transepts of a large church, containing a series of windows. It is clear of the roofs of the aisles and admits light to the central parts of the building. the windows in the clerestory of a church or similar windows in another building. a raised section of roof running down the center of a railroad car, with small windows or ventilators.