clerestoryPronunciation: /ˈklɪəˌstɔːri/ (US also clearstory)Definition of clerestory noun (plural clerestories) the upper part of the nave, choir, and transepts of a large church, containing a series of windows. a series of windows in another large building that are similar to those in a clerestory. a raised section of roof running down the centre of a railway carriage, with small windows or ventilators. Origin: late Middle English: from clear + storeyclerestory in other Oxford dictionaries Definition of clerestory in the US English dictionary