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

These are your consumers, employees, and future leaders who represent unfathomable potential. —Marcela Manjarrez, Forbes, 9 Sep. 2024

That’s true even of D’Onofrio’s unfathomable serial killer. —Alison Foreman, IndieWire, 15 Aug. 2024

Even more impressively, ChinaDaily reported at the time that CATL believes the battery tech is capable of supporting a currently unfathomable 2,000- to 3,000-km (1,240 to 1,865-mile) range in an 8-ton electric aircraft within just a few years' time. —New Atlas, 8 Aug. 2024

The results prove that these unfathomable objects can be constructed in any dimension at a fraction of the size of more traditional rolling shapes, such as circles or spheres. —Max Springer, Scientific American, 7 Aug. 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