cloister has 1 distinct synonym spread across 1 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
surround with a cloister, as of a garden
surround with a cloister
“cloister the garden”
seclude from the world in or as if in a cloister
“She cloistered herself in the office”
Synonyms, antonyms and the broader and narrower relations for cloister come from Princeton University’s WordNet. Full sources and licences.
residence that is a place of religious seclusion (such as a monastery)
a courtyard with covered walks (as in religious institutions)