from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Difficult or impossible to understand; incomprehensible: unfathomable theories.
  • adj. Difficult or impossible to measure: the unfathomable depths.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. impossible to fathom or understand; incomprehensible
  • adj. difficult to penetrate.

from The Century Dictionary and Cyclopedia

  • Incapable of being fathomed or sounded; too deep to be measured; hence, not capable of being sounded by thought or comprehended.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. of depth; not capable of being sounded or measured
  • adj. resembling an abyss in depth; so deep as to be unmeasurable
  • adj. impossible to come to understand


from Wiktionary, Creative Commons Attribution/Share-Alike License

un- +‎ fathomable


  • When he looked up, his wife was staring down at him, her expression unfathomable in the darkness.

    Family Blessings

  • He just looked at her, his expression unfathomable.

    Life Support

  • Ferris had never ceased to wonder at what he called the unfathomable innocence of his wife, and he liked to go over all the points of their former life in Venice, and bring home to himself the utter simplicity of her girlish ideas, motives, and designs, which both confounded and delighted him.

    A Foregone Conclusion

  • But these latest outrages — arrogant failed business executives raking in unfathomable bonuses from the taxpayers — have an "enough is enough" quality to them.

    The outrage quotient rises

  • Equally unfathomable is the fact that Dave should come in fourth in the "Arena Magazine Poll".

    Waiting For Guido ...

  • It's going to take a while to go through all of the documents, and certainly there will be some embarrassing, mystifying and and just plain unfathomable information gleaned from them.

    The Dump

  •  His expression unfathomable, he continued to watch, and then turned abruptly, his progress across the courtyard fluttering the doves into noisy protest.

    Falcon's Prey

  • Because I use it a lot whether you do or not — all the way down from my cabin to this Palace Of Authority, where you do not even have decent coffee, which I find puzzling or a better word unfathomable!

    Self-Destruction, Vol. 1

  • LEVS: Yeah, and we were just talking about the idea of unfathomable numbers that applies to the deaths and the toll that we're hearing and everything that's happening with the bombings.

    CNN Transcript Feb 4, 2007

  • The idea that the world champion might not be able to defend his title was unfathomable.

    One of a Kind


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