1. Pertaining to being uncertain or beyond recognition: The dead body had been in the lake for so long that it was quite incognoscible and so no one was able to identify it.
2. A reference to something that is incapable of being perceived or understood: In the advanced math class at college, some of the topics the professor was talking about were very incognoscible for some members of the class because they couldn’t understand what he was presenting to them.