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[fath-uh m]
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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
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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.
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Origin of fathom

before 900; Middle English fathme, Old English fæthm span of outstretched arms; cognate with German Faden six-foot measure, Old Norse fathmr; akin to patent
Related formsfath·om·a·ble, adjectivefath·om·er, nounun·fath·om·a·ble, adjectiveun·fath·omed, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words


Examples from the Web for fathoming

Historical Examples

  • He looked at her for a moment, fathoming the purport of what she said.

    The Trampling of the Lilies

    Rafael Sabatini

  • This difference is beyond the fathoming line of human thought.

  • In fact he had thrown himself in his hands for the purpose of fathoming his plots.

  • The doctor was fathoming Josephine, for the benefit of his companion.

    White Lies

    Charles Reade

  • My affection hampers me from fathoming Frank's inner-most thoughts.

    Old Mr. Wiley

    Fanny Greye La Spina

British Dictionary definitions for fathoming


  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
  3. forestry a unit of volume equal to six cubic feet, used for measuring timber
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verb (tr)
  1. to measure the depth of, esp with a sounding line; sound
  2. to penetrate (a mystery, problem, etc); discover the meaning of
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Derived Formsfathomable, adjectivefathomer, noun

Word Origin

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

Word Origin and History for fathoming



Old English fæðm "length of the outstretched arm" (a measure of about six feet), also "arms, grasp," and, figuratively "power," from Proto-Germanic *fathmaz "embrace" (cf. Old Norse faðmr "embrace, bosom," Old Saxon fathmos "the outstretched arms," Dutch vadem "a measure of six feet"), from PIE *pot(e)-mo-, from root *pete- "to spread, stretch out" (see pace (n.)). There are apparent cognates in Old Frisian fethem, German faden "thread," which OED explains by reference to "spreading out."

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Old English fæðmian "to embrace, surround, envelop;" see fathom (n.). The meaning "take soundings" is from c.1600; its figurative sense of "get to the bottom of, understand" is 1620s. Related: Fathomed; fathoming.

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Online Etymology Dictionary, © 2010 Douglas Harper