unfathomable

adjective

un·​fath·​om·​able ˌən-ˈfa-t͟hə-mə-bəl 

: not capable of being fathomed:

a

: immeasurable

b

: impossible to comprehend

unfathomably

ˌən-ˈfa-t͟hə-mə-blē 

adverb

Synonyms

• bottomless
• boundless
• endless
• fathomless
• horizonless
• illimitable
• immeasurable
• immensurable
• indefinite
• infinite
• limitless
• measureless
• unbounded
• unlimited

Examples of unfathomable in a Sentence

His behavior is completely unfathomable.

the unfathomable reaches of space

Recent Examples on the Web

For instance, the decrease in price and even physical size of core elements like batteries, processing chips and bandwidth have allowed for the creation of devices that provide previously unfathomable experiences. —Jon Kirchner, Forbes, 10 Dec. 2024

The circumstances of your mother’s death are unfathomable for anyone who’ll read this. —Mikey O'Connell, The Hollywood Reporter, 6 Dec. 2024

This represents [an] unfathomable potential for establishing industries on the continent, not only to counterweight the Chinese economy, but to lock in a future market for all the top brands of EU and U.S. businesses. —Paul Tilsley, Fox News, 2 Dec. 2024

These days, homeownership is no easy feat; what once was a common milestone for generations of adults now feels unfathomable for Gen Z and millennials. —Madeline Bilis, Architectural Digest, 21 Nov. 2024

Word History

First Known Use

1640, in the meaning defined above

Kids Definition

unfathomable

adjective

un·​fath·​om·​able ˌən-ˈfat͟h-ə-mə-bəl 

: not capable of being fathomed:

a

: immeasurable

b

: impossible to understand