WordNet records no synonym and no antonym for case study. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
a careful study of some social unit (as a corporation or division within a corporation) that attempts to determine what factors led to its success or failure
a detailed analysis of a person or group from a social or psychological or medical point of view
Synonyms, antonyms and the broader and narrower relations for case study come from Princeton University’s WordNet. Full sources and licences.