What does impenetrable mean in crosswords?

impenetrable means: impossible to understand

Which crossword clues can have impenetrable as the answer?

Possible clues for impenetrable include "Hard to enter".

Word entry · 12 letters

Best crossword clue

"Hard to enter"

12 letters · collected on this word page

12 lettersSorted abeeeilmnprtStarts with IEnds with E1 clues

1I2M3P4E5N6E7T8R9A10B11L12E

01“Hard to enter”12 letters

Not quite right?

I___________