Definition of fathom in English:



  • A unit of length equal to six feet (1.8 metres), chiefly used in reference to the depth of water.

    ‘sonar says that we're in eighteen fathoms’
    • ‘A rock had suddenly risen out of the depths not three fathoms from the point of the bow.’
    • ‘It looms towards us, shrouded by fathoms of blue water.’
    • ‘With great sadness they buried him in 2,700 fathoms of water, some 300 miles from Tahiti.’
    • ‘On March 23, 1875, 13 days after leaving Nares Harbor, soundings indicated a depth of 4,475 fathoms or about 27,000 feet.’
    • ‘As the standard length of rope required just to drop anchor was 120 fathoms, the market was a big one.’
    • ‘The depth sounder tells him how deep his traps are, and the deepest ones we we'll hit today are in about 40 fathoms, or 240 feet, of water.’
    • ‘To their horror, the engine of the boat failed in 23 fathoms of water.’
    • ‘They are reported to be capable of diving to depths of 100 to 150 fathoms and remain submerged for up to 15 minutes.’
    • ‘We trolled a zig-zag course along a drop-off, the deep water hitting 150 fathoms.’
    • ‘The anchor plummeted down nearly ten fathoms; it is deep, but so sheltered that not much scope is necessary.’
    • ‘This lay on the bed of the South China Sea for almost 200 years at a depth of 17 fathoms.’
    • ‘This shark, common in deep waters, is occasionally found in depths as shallow as 20 fathoms.’
    • ‘All nets had to be licensed annually and were taxed at the rate of five dollars for every net 65 fathoms in length or smaller.’
    • ‘If your boat is in the water and cannot be trailered, move it offshore to waters over 200 fathoms deep as soon as a Tsunami Warning is declared.’
    • ‘I saw real cities of the surface world, lying in ruins under a thousand fathoms of water.’
    • ‘The maximum reported depth reached by the species is 194 fathoms.’
    • ‘A couple of miles off Punta Arena the water is said to drop away into 100 fathoms or 600-feet, and double that distance just beyond the Pulmo Shoals.’
    • ‘He is still miles and fathoms and nautical miles and light years ahead of everyone else in baseball.’
    • ‘The first column is the circumference in inches and the other three columns are fathoms, feet, and inches.’
    • ‘At a depth of fifteen fathoms it was six feet wide and contained 76% copper.’


  • 1[usually with negative] Understand (a difficult problem or an enigmatic person) after much thought.

    ‘the locals could not fathom out the reason behind his new-found prosperity’
    [with clause] ‘he couldn't fathom why she was being so anxious’
    • ‘I would go to any extent in my art to fathom the mystery of humankind's existence.’
    • ‘Can you even fathom what goes into this kind of self-inflicted torture?’
    • ‘I still couldn't fathom why they held such a presence over the school.’
    • ‘But I can't fathom anyone reading stories like this and not feeling the sting and burn of utter, abject shame.’
    • ‘How could you possibly fathom how much he cares for you?’
    • ‘I just can't fathom people who could have a quiet life, who don't have to be controversial for a living, but do it anyway.’
    • ‘She just can't seem to fathom the idea that she's a good player.’
    • ‘It really did give one's mind a good exercise, trying to fathom out the clues, whether they be ‘red herrings’ or helpful hints.’
    • ‘He spent his entire life trying to fathom the mysteries of life: what is virtue?’
    • ‘Harrison looked so strong that they couldn't fathom him breaking down.’
    • ‘Even if we were just friends, I still didn't want to fathom another girl in the picture.’
    • ‘But I still couldn't quite fathom the idea of living with Dad.’
    • ‘They couldn't even fathom what I was feeling.’
    • ‘He could never fathom ever giving up his absolute free will.’
    • ‘They can't fathom that fellow members of democratic societies would not share their struggle with them.’
    • ‘Immediately, the glacial glare seemed to diminish… though Sammy couldn't fathom why.’
    • ‘I just couldn't fathom why he would want to do such a thing.’
    • ‘You can analyze a Mozart piano concerto note by note and still not fathom the genius of the whole piece.’
    • ‘She didn't have time to fathom the mystery of books, though.’
    • ‘She couldn't fathom him having any of those anymore.’
    understand, comprehend, work out, fathom out, make sense of, grasp, catch, follow, perceive, make out, penetrate, divine, search out, ferret out, puzzle out, take in, assimilate, absorb, get to the bottom of
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  • 2Measure the depth of (water)

    ‘an attempt to fathom the ocean’
    • ‘In the middle of this temple complex, there is an ancient pond, fed by the waters sprouting from its bed; it has been claimed that the depth of this pond has never been fathomed.’
    measure the depth of, sound, plumb, probe
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Old English fæthm, of Germanic origin; related to Dutch vadem, vaam and German Faden six feet. The original sense was ‘something which embraces’, (plural) ‘the outstretched arms’; hence, a unit of measurement based on the span of the outstretched arms, later standardized to six feet.