1911 Encyclopedia Britannica
(Med. Lat. ambulatorium, a place for walking, from ambulare, to walk), the covered passage round a cloister; a term applied sometimes to the procession way round the east end of a cathedral or large church and behind the high altar.
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Chisholm, Hugh, General Editor. Entry for 'Ambulatory'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/a/ambulatory.html. 1910.