The term 'Impossible to Understand' can be described by three crossword solutions: UNFATHOMABLE (12 letters), Clearasmud (10 letters), and INSCRUTABLE (11 letters). UNFATHOMABLE means something that is too deep or complex to comprehend, Clearasmud is an old English phrase meaning something that is impossible to understand, and INSCRUTABLE means something that is impossible to interpret or comprehend. All three words describe something that is impossible to understand.