Unfathomable

Origin

- + fathomable

Full definition of unfathomable

Adjective

1. impossible to fathom or understand; incomprehensibleThe sheer numbers they attacked with were unfathomable.
• 2013, April 9, Andrei Lankov, Stay Cool. Call North Korea’s Bluff., 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.
2. difficult to penetrate.

Antonyms

• fathomable