[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
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

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 for unfathomed

ethereal, immense, infinite, undetermined, vast, wide

Examples from the Web for unfathomed

Historical Examples of unfathomed

  • Here is the natural—but there is the vast, unfathomed supernatural.

  • No man so amphibious has since arisen through the unfathomed tide of time.

    Mary Anerley

    R. D. Blackmore

  • The stream begins in mystery, and ends in unfathomed darkness.

  • There was only one thought which could set him aflame, and that was the thought of the unfathomed might of man.

    Emerson and Other Essays

    John Jay Chapman

  • What brought him to bustling, sunny Naples, was an unfathomed mystery.

    A Love Story

    A Bushman

British Dictionary definitions for unfathomed


  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
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
Derived Formsfathomable, adjectivefathomer, noun

Word Origin for fathom

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 unfathomed

1620s, from un- (1) "not" + past participle of fathom.



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."



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.

Online Etymology Dictionary, © 2010 Douglas Harper