noun

• (chiefly nautical, historical, US) A man's armspan, generally reckoned to be six feet (about 1.8 metres). Later used to measure the depth of water, but now generally replaced by the metre outside American usage.
  "[T]he ſhipmen deemed that they drew neere to ſome countrey: And ſounded, and found it twentie fathoms: and when they had gone a little further, they ſounded againe, and found it fifteene fathoms."
• (chiefly nautical, historical, US) A man's armspan, generally reckoned to be six feet (about 1.8 metres). Later used to measure the depth of water, but now generally replaced by the metre outside American usage.
• (nautical, US) A measure of distance to shore: the nearest point to shore at which the water depth is the value quoted.
  "After we'd rowed for an hour, we found ourselves stranded ten fathoms from shore."
• (figuratively)

verb

• (transitive)
• (transitive)
• (transitive)
  "I can’t for the life of me fathom what this means."
• (transitive)