The crossword clue "impossible to understand" can have several common answers depending on the number of letters:
- UNFATHOMABLE (12 letters)
- UNINTELLIGIBLE (14 letters)
- BAFFLING (8 letters)
- CLEARASMUD (10 letters)
- FATHOMLESS (10 letters)
These words all convey the meaning of something that is difficult or impossible to understand.