Uncanny describes that which unsettles us, such as disquieting observations, or mysterious situations and circumstances. Strip the word of its prefix, though, and you're left with canny, a word that can be used as a synonym for clever and prudent. UNCANNY definition: 1. strange or mysterious, often in a way that is slightly frightening: 2. strange or mysterious…. Learn more. Uncanny definition: Mysterious or impossible to explain, especially when causing uneasiness or astonishment. Definition of uncanny adjective in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.