/ ˈklɔɪstə(r); NAmE / noun
1.
[ C , usually pl. ] a covered passage with arches around a square garden, usually forming part of a cathedral , convent or monastery
2.
[ sing. ] life in a convent or monastery
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WORD ORIGIN
Middle English (in the sense place of religious seclusion ): from Old French cloistre , from Latin claustrum , clostrum lock, enclosed place, from claudere , to close.