English Reference

Word

unfathomable

Phoneticsun·fath·omable

US/ənˈfæðəməbəɫ/

UK/ʌnfˈæðəməbəl/

Definition

adj. so difficult to understand that you cannot see the reason for it. You use this when something is completely confusing or mysterious.

adj. impossible to understand or explain; beyond the reach of human comprehension. Often used to describe complex problems, deep emotions, or vast distances.

Examples

“The reason for his sudden change was unfathomable to everyone.”

“The depth of the ocean is unfathomable, with many parts still unexplored by modern technology.”

“The sudden collapse of the bridge was an unfathomable tragedy that left the entire community in shock and demanded a complete review of safety standards.”

Examples

simple

“The reason for his sudden change was unfathomable to everyone.”

contextual

“The depth of the ocean is unfathomable, with many parts still unexplored by modern technology.”

complex

“The sudden collapse of the bridge was an unfathomable tragedy that left the entire community in shock and demanded a complete review of safety standards.”

Real-World Examples

“A notebook and pen lie beside me on the sand as I, too, attempt to read the waves, to find meaning in their unfathomable churn.”
The Guardian · 23 Aug 2026
“Listening to them is like swimming in an ocean of unfathomable wisdom.”
Aeon · 20 Aug 2026

Etymology

From un- (prefix meaning ‘not’) + fathom (“to measure the depth of (water); (figurative) to deeply understand (someone or something)”) + -able (suffix forming adjectives denoting things not able or fit to be done).

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

Related words

This entry

Level
C1 · Advanced
Frequency
Occasional
Updated

Scan code

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English Reference