[ fath-uhm ]
See synonyms for: fathomfathomedfathomingfathoms on Thesaurus.com

noun,plural fath·oms, (especially collectively) fath·om.
  1. a unit of length equal to six feet (1.8 meters): used chiefly in nautical measurements. Abbreviation: fath

verb (used with object)
  1. to measure the depth of by means of a sounding line; sound.

  2. to penetrate to the truth of; comprehend; understand: to fathom someone's motives.

Origin of fathom

First recorded before 900; Middle English fathme, Old English fæthm “span of outstretched arms”; cognate with German Faden “six-foot measure,” Old Norse fathmr; akin to Latin patēre “to stand open” (see patent)

Other words from fathom

  • fath·om·a·ble, adjective
  • fath·om·er, noun
  • un·fath·om·a·ble, adjective
  • un·fath·omed, adjective

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use fathom in a sentence

British Dictionary definitions for fathom


/ (ˈfæðəm) /

  1. a unit of length equal to six feet (1.829 metres), used to measure depths of water

  2. mining a unit of volume usually equal to six cubic feet, used in measuring ore bodies

  1. forestry a unit of volume equal to six cubic feet, used for measuring timber

  1. to measure the depth of, esp with a sounding line; sound

  2. to penetrate (a mystery, problem, etc); discover the meaning of

Origin of fathom

Old English fæthm; related to Old Frisian fethem outstretched arms, Old Norse fathmr embrace, Old High German fadum cubit, Latin patēre to gape

Derived forms of fathom

  • fathomable, adjective
  • fathomer, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012