A more thorough explanation:

Definition: Casus rarior (kay-suhss rair-ee-or) is a Latin term used to describe an exceptional case.

Example: In legal terms, a casus rarior could be a situation that has never been encountered before, making it difficult to apply existing laws and regulations. For instance, a case where a person is born with both male and female reproductive organs would be considered a casus rarior.

Explanation: The example illustrates how a casus rarior is an exceptional case that is not common and may not have a clear solution. In this case, the legal system may struggle to determine the person's gender and how to apply laws related to gender identity.