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unfathomable

American  
[uhn-fath-uh-muh-buhl] / ʌnˈfæð ə mə bəl /

adjective

  1. not able to be fathomed, or completely understood; incomprehensible.

    heroism in the face of unfathomable conflict.

  2. not able to be measured with a sounding line, or fathomed.

    unfathomable depths of the ocean.
unfathomable British  
/ ʌnˈfæðəməbəl /

adjective

  1. incapable of being fathomed; immeasurable

  2. incomprehensible

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

  • unfathomableness noun
  • unfathomably adverb

Etymology

Origin of unfathomable

First recorded in 1610–20; un- 1 ( def. ) + fathom ( def. ) + -able ( def. )

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.