Definition of "fathom"

(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.  quotations

(nautical, US) A measure of distance to shore: the nearest point to shore at which the water depth is the value quoted.  quotations  examples

(figuratively)

1. (chiefly in the plural) An unspecified depth.  examples

2. (archaic or obsolete) Depth of insight; mental reach or scope.  quotations

   Quotations

   • Another of his fathome they haue not / To leade their buſineſſe, […]

     c. 1603–1604 (date written), William Shakespeare, The Tragœdy of Othello, the Moore of Venice. […] (First Quarto), London: […] N[icholas] O[kes] for Thomas Walkley, […], published 1622, [Act I, scene i]

(obsolete)

1. The act of stretching out one's arms away from the sides of the torso so that they make a straight line perpendicular to the body.  examples

2. Someone or something that is embraced.  quotations  examples

   Quotations

   • Thy Bride, thy choice, thy vvife, / She that is novv thy fadom, […] Kneele at thy feete, obay in euerie thing, / So euerie Father is a priuate King.

     1601 (first performance), Thomas Dekker, Satiro-mastix. Or The Untrussing of the Humorous Poet. […], London: […] [Edward Allde] for Edward White, […], published 1602, signature E, verso

3. (figuratively) Control, grasp.  quotations  examples

   Quotations

   • So; novv knovv I vvhere I am, me thinkes already / I graſpe beſt part of the Autumnian bleſſing / In my contentious fadome, […]

     1604 (first performance), [Thomas Middleton], “Inductio”, in Michaelmas Terme. […], London: […] [Thomas Purfoot and Edward Allde] for A[rthur] I[ohnson] […], published 1607, signature A2, recto

   • Yes: / you have blovvne his ſvvolne pride to that vaſtnes, / as he beleeves the earth is in his fadom, / this makes him qute forget his humble Being: […]

     1622 May 24 (licensing date), John Fletcher, Philip Massinger, “The Prophetesse”, in Comedies and Tragedies […], London: […] Humphrey Robinson, […], and for Humphrey Moseley […], published 1647, Act II, scene i, page 29

(transitive)

1. (also figuratively) To measure the depth of (water); to take a sounding of; to sound.  examples

2. (archaic or obsolete) To encircle (someone or something) with outstretched arms; specifically, to measure the circumference or (rare) length of something.

3. (figuratively) Often followed by out: to deeply understand (someone or something); to get to the bottom of.  quotations  examples

   Quotations

   • Otamendi’s selection ahead of Vincent Kompany was difficult to fathom and, apart from Fernandinho, City’s line-up was otherwise filled with attacking players.

     2018 April 10, Daniel Taylor, “Liverpool go through after Mohamed Salah stops Manchester City fightback”, in The Guardian (London)‎

4. (obsolete) To embrace (someone or something).

(intransitive)

1. To measure a depth; to sound.  examples

2. (figuratively) To conduct an examination or inquiry; to investigate.  examples