adjective
-
incapable of being fathomed; immeasurable
-
incomprehensible
Other Word Forms
- unfathomableness noun
- unfathomably adverb
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
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
"To Kill a Mockingbird" by Harper Lee, Chapters 7–11
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
"The Black Cat" by Edgar Allan Poe
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
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.
Buying a $1 million building — even if you’re sharing it with tenants — may simply feel unfathomable to them.
From MarketWatch • Apr. 3, 2026
Mario Jardel scored at an unfathomable rate, until he rocked up at Bolton.
From BBC • Mar. 3, 2026
In the movie, Charli contends with the unfathomable triumph of “Brat” while fielding brand deal offers and label demands that reek of the capitalist desperation to extend the “Brat” era as long as possible.
From Salon • Feb. 8, 2026
The steely husks stood sentinel over unfathomable loss for weeks or months until they were towed away and sold as scrap.
From Los Angeles Times • Jan. 26, 2026
The presumed deception, including within their own family, is so deep as to be unfathomable.
From "American Spirits" by Barb Rosenstock
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.
