adjective
-
incapable of being fathomed; immeasurable
-
incomprehensible
Other Word Forms
Etymology
Origin of unfathomable
First recorded in 1610–20; un- 1 ( def. ) + fathom ( def. ) + -able ( def. )
Explanation
Unfathomable means impossible to ever understand. For most people, the field of quantum mechanics is unfathomable. Fathoms are seafaring units of measure equaling about six feet. So something that is unfathomable is also immeasurable, especially when it comes to depth. If your sonar isn't bouncing anything back to you, you're dealing with an unfathomable distance. Metaphorically, unfathomable can refer to something that resembles an abyss, some figurative notion that's so deep you can't even measure it.
Vocabulary lists containing unfathomable
The Outsiders
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"To Kill a Mockingbird" by Harper Lee, Chapters 7–11
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"The Black Cat" by Edgar Allan Poe
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
A statement released by his parents said Haines had been "our friend for more than 20 years and what happened to her yesterday is devastating and unfathomable", The Age newspaper reported.
From Barron's ● Oct. 20, 2026
But that’s the point of “Rock*.” It’s a lopsided hymn of praise to music—all music—that changes lives for very particular and ultimately unfathomable reasons.
From The Wall Street Journal ● Sep. 18, 2026
But with a quarter-century of hindsight, asking the mayor to remove himself from a solemn commemoration of the greatest tragedy to ever occur in his city is unfathomable.
From Salon ● Sep. 11, 2026
Despite the failings in Jaafri's care, "and for reasons which remain unfathomable", the death was not reported to him by doctors at the hospital, nor the medical examiner, the coroner said.
From BBC ● Aug. 18, 2026
But who could live in that leafy hair? that unfathomable skin?
From "Jazz" by Toni Morrison
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Get a wordDefinitions 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.
