CLERESTORY

n. upper wall and row of windows in a cathedral (Architecture)

Clerestory ( lit. clear storey, also clearstory, clearstorey, or overstorey) is an architectural term denoting an upper level of a Roman basilica or of the nave of a Romanesque or Gothic church, the walls of which rise above the rooflines of the lower aisles and are pierced with windows. The Romans also used clerestories in their basilica-like baths and palaces, and probably derived the clerestory from the Hellenistic architecture of the Greeks. The clerestory originated in the temples of Egypt. It is also used to denote a style of railway rolling stock (predominantly passenger), for example the Great Western Railway Clerestory carriage of the Victorian era where the windows in the roof 'cupola' provided access to, and ventilation for, the vehicle's gas lighting.
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Noun
1. part of an interior wall rising above the adjacent roof with windows admitting light
(synonym) clearstory
(hypernym) window

(n.)
The upper story of the nave of a church, containing windows, and rising above the aisle roofs.
  

(n.)
Same as Clearstory.
  

Synonyms and related words:
entresol, first floor, flat, floor, ground floor, level, mezzanine, mezzanine floor, rez-de-chaussee, ridgepole, roof, roofpole, rooftop, story, street floor, surface, top, top floor, top side, topside, topsides, upper side, upside