noun
fathom
FATHM
noun
1
A unit of length equal to six feet (about 1.8 metres), traditionally used to measure the depth of water.
"The wreck lies at a depth of about forty fathoms."
verb
1
To understand something fully, especially something puzzling or complicated.
"I still can't fathom why he quit such a great job."
"She tried to fathom the meaning behind his cryptic message."
How to Use Fathom
Learner’s notesIn plain EnglishEither a nautical unit of depth, or (more commonly today) to fully understand something confusing.
Common mistake
In modern everyday speech, "fathom" almost always means "to understand" — the measurement sense is mostly limited to sailing and diving contexts.
Common pairings
fathom out
hard to fathom
unable to fathom
Word Forms
fathomed past tense, fathoms plural, fathoms singular
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The wreck lies at a depth of about forty _____.
Etymology
From Old English fæþm, originally meaning "outstretched arms" or "embrace" — the span of a person's arms was once used to measure length.