# unfathomable

/ənˈfæðəməbəɫ/ (US) · /ʌnfˈæðəməbəl/ (UK) · CEFR C1 · Adjective

Source: https://englishreference.com/word/unfathomable
Updated: 2026-05-19

## Definition

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

For teachers: 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.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.