WordNet sense 1 (a special set of circumstances):

event

WordNet sense 2 (the quantity contained in a case):

caseful

WordNet sense 3 (a person who is subjected to experimental or other observational procedures; someone who is an object of investigation):

subject, subject, guinea pig

WordNet sense 4 (a person of a specified kind (usually with many eccentricities)):

character, eccentric, type

WordNet sense 5 (an occurrence of something):

example, instance

WordNet sense 6 (nouns or pronouns or adjectives (often marked by inflection) related in some way to other words in a sentence):

grammatical case

WordNet sense 7 (an enveloping structure or covering enclosing an animal or plant organ or part):

sheath

WordNet sense 8 (the housing or outer covering of something):

casing, shell

WordNet sense 9 (bed linen consisting of a cover for a pillow):

pillowcase, slip

WordNet sense 10 (a glass container used to store and display items in a shop or museum or home):

showcase, vitrine, display case

WordNet sense 11 (enclose in, or as if in, a case):

encase, incase

WordNet sense 12 (a comprehensive term for any proceeding in a court of law whereby an individual seeks a legal remedy):

cause, lawsuit, suit, causa