unfathomable

adjective

un·​fath·​om·​able ˌən-ˈfa-t͟hə-mə-bəl How to pronounce unfathomable (audio)
Synonyms of unfathomable
: not capable of being fathomed:
a
: immeasurable
… the unfathomable darkness of empty space.—H. G. Wells
b
: impossible to comprehend
unfathomable motives/reasons
unfathomably
ˌən-ˈfa-t͟hə-mə-blē How to pronounce unfathomable (audio)
adverb

Synonyms of unfathomable

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Examples of unfathomable in a Sentence

His behavior is completely unfathomable. the unfathomable reaches of space
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
On behalf of myself, our staff, and the Board of Directors, we are entirely devastated by this unfathomable loss to Country Music and the entire world. — Steven J. Horowitz, Variety, 25 Aug. 2026 Building a racetrack in the middle of a city comes with an unfathomable number of logistical challenges. — Adam Kilgore, New York Times, 20 Aug. 2026 The blur outside becomes enveloping and unfathomable; the universe inside the car evolves as the friends invent tension-defusing rituals to keep from screaming at one another. — Amy Nicholson, Los Angeles Times, 19 Aug. 2026 At times, Columbia House offered deals that now seem unfathomable, like 12 CDs for a penny (with the catch being that purchasers have to start a subscription, which was often challenging to cancel). — Virginia Chamlee, PEOPLE, 18 Aug. 2026 See All Example Sentences for unfathomable

Word History

First Known Use

1640, in the meaning defined above

Time Traveler
The first known use of unfathomable was in 1640

Browse Nearby Words

unfatherly
unfathomable
unfathomably
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Cite this Entry

“Unfathomable.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/unfathomable. Accessed 1 Sep. 2026.

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Kids Definition

unfathomable

adjective
un·​fath·​om·​able ˌən-ˈfat͟h-ə-mə-bəl How to pronounce unfathomable (audio)
: not capable of being fathomed:
a
: immeasurable
b
: impossible to understand
Last Updated: - Updated example sentences
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