term:

Sui Generis

sui generis adj

[Latin, of its own kind]
: constituting a class alone
: unique or particular to itself [the lawyer's…ad that makes no distinction among various legal and factual nuances in each sui generis case has the potential to mislead "National Law Journal"]

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.