- Impossible to fathom or understand; incomprehensible.
- The sheer numbers they attacked with were unfathomable.
2013 April 9, Andrei Lankov, “Stay Cool. Call North Korea’s Bluff.”, in New York Times:
- Suggestions that those leaders are irrational and their decisions unfathomable are remarkably shallow. North Korea is not a theocracy led by zealots who preach the rewards of the afterlife.
- Difficult to penetrate.
impossible to fathom; incomprehensible
difficult to penetrate