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.
I can’t help but wonder if it’s partly living with all this that allows you to create a record of such unfathomable beauty.
From Los Angeles Times ● Jul. 21, 2026
“The idea that we’re competing with the market would have been unfathomable a few years ago,” said Margaret Salazar, CEO of Reach Community Development Corporation, one of Portland’s largest affordable housing providers.
From Salon ● Jul. 4, 2026
“It’s unfathomable that we’re actually playing in this huge tournament,” Curaçao coach Dick Advocaat said.
From The Wall Street Journal ● Jun. 25, 2026
"I think the best word that people have used to me is 'unfathomable'. It is unfathomable that this should have happened," she says.
From BBC ● Jun. 9, 2026
To Moody, this kind of existence was all but unfathomable.
From "Little Fires Everywhere" by Celeste Ng
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.
