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’
    • ‘I saw real cities of the surface world, lying in ruins under a thousand fathoms of water.’
    • ‘At a depth of fifteen fathoms it was six feet wide and contained 76% copper.’
    • ‘The maximum reported depth reached by the species is 194 fathoms.’
    • ‘On March 23, 1875, 13 days after leaving Nares Harbor, soundings indicated a depth of 4,475 fathoms or about 27,000 feet.’
    • ‘To their horror, the engine of the boat failed in 23 fathoms of water.’
    • ‘This lay on the bed of the South China Sea for almost 200 years at a depth of 17 fathoms.’
    • ‘A rock had suddenly risen out of the depths not three fathoms from the point of the bow.’
    • ‘The anchor plummeted down nearly ten fathoms; it is deep, but so sheltered that not much scope is necessary.’
    • ‘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.’
    • ‘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.’
    • ‘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.’
    • ‘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.’
    • ‘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.’
    • ‘With great sadness they buried him in 2,700 fathoms of water, some 300 miles from Tahiti.’
    • ‘We trolled a zig-zag course along a drop-off, the deep water hitting 150 fathoms.’
    • ‘It looms towards us, shrouded by fathoms of blue water.’
    • ‘They are reported to be capable of diving to depths of 100 to 150 fathoms and remain submerged for up to 15 minutes.’
    • ‘As the standard length of rope required just to drop anchor was 120 fathoms, the market was a big one.’


[with object]
  • 1usually 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 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?’
    • ‘Harrison looked so strong that they couldn't fathom him breaking down.’
    • ‘He could never fathom ever giving up his absolute free will.’
    • ‘Can you even fathom what goes into this kind of self-inflicted torture?’
    • ‘It really did give one's mind a good exercise, trying to fathom out the clues, whether they be ‘red herrings’ or helpful hints.’
    • ‘Even if we were just friends, I still didn't want to fathom another girl in the picture.’
    • ‘I would go to any extent in my art to fathom the mystery of humankind's existence.’
    • ‘He spent his entire life trying to fathom the mysteries of life: what is virtue?’
    • ‘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.’
    • ‘They couldn't even fathom what I was feeling.’
    • ‘I just couldn't fathom why he would want to do such a thing.’
    • ‘She didn't have time to fathom the mystery of books, though.’
    • ‘You can analyze a Mozart piano concerto note by note and still not fathom the genius of the whole piece.’
    • ‘They can't fathom that fellow members of democratic societies would not share their struggle with them.’
    • ‘She couldn't fathom him having any of those anymore.’
    • ‘Immediately, the glacial glare seemed to diminish… though Sammy couldn't fathom why.’
    • ‘She just can't seem to fathom the idea that she's a good player.’
    • ‘But I still couldn't quite fathom the idea of living with Dad.’
    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
    View synonyms
  • 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
    View synonyms


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.