This category is for languages deliberately designed to be often unusable, unimplementable, or both. The stress is on "deliberately". A language that is unsuitable for actual programming not by intention but merely (1) due to its inventor's ineptitude, or (2) due to lack of industry support or acceptance by the computer science community, is not obfuscated. Thus this category does not list Pascal, Modula, Ada, or C#.
Obfuscated languages are of two types, those that are: (1) Nothing more, or less, than elaborate jokes; example: Intercal is not much more than a thinking person's diversion, albeit a hilariously funny and impressively creative one. (2) Thoughtful and systematic explorations of the subtleties of programming language and algorithm design, or of the theory of computability.