noun, plural fathoms (especially collectively) fathom.
a unit of length equal to six feet (1.8 meters): used chiefly in nautical measurements. Abbreviation: fath
verb (used with object)
to measure the depth of by means of a sounding line; sound.
to penetrate to the truth of; comprehend; understand: to fathom someone's motives.

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

fathomable, adjective
fathomer, noun
unfathomable, adjective
unfathomed, adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To fathom
World English Dictionary
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
3.  forestry a unit of volume equal to six cubic feet, used for measuring timber
4.  to measure the depth of, esp with a sounding line; sound
5.  to penetrate (a mystery, problem, etc); discover the meaning of
[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 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
Word Origin & History

O.E. fæðm "length of the outstretched arm" (a measure of about six feet), also "arms, grasp," and, figuratively "power," from P.Gmc. *fathmaz "embrace" (cf. O.N. faðmr "embrace, bosom," O.S. fathmos "the outstretched arms," Du. vadem "a measure of six feet"), from PIE *pot-/*pet- denoting
"stretching out" (cf. Gk. petalon "leaf," L. patere "to be open"). The verb meaning of "take soundings" is c.1600; its figurative sense of "get to the bottom of, understand" is 1620s. Related: Fathomed; fathoming.
Online Etymology Dictionary, © 2010 Douglas Harper
Cite This Source
Bible Dictionary

Fathom definition

(Old A.S. faethm, "bosom," or the outstretched arms), a span of six feet (Acts 27:28). Gr. orguia (from orego, "I stretch"), the distance between the extremities of both arms fully stretched out.

Easton's 1897 Bible Dictionary
Cite This Source
Encyclopedia Britannica


old English measure of length, now standardized at 6 feet (1.83 metre), which has long been used as a nautical unit of depth. The longest of many units derived from an anatomical measurement, the fathom originated as the distance from the middle fingertip of one hand to the middle fingertip of the other hand of a large man holding his arms fully extended. The name comes from the Old English faedm or faethm, meaning outstretched arms

Learn more about fathom with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Example sentences
He could not understand the temptation that had come to him nor could he fathom
  the reason for its coming.
Some outsiders might still believe they have savvy that even insiders can't
Besides, he couldn't fathom collecting money for something he viewed as
  unfinished work that required the contribution of others.
Its solvency rests on a relationship with its neighbour that is impossible to
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature