unfathomable

From un- (prefix meaning ‘not’) +‎ fathom (“to measure the depth of (water); (figurative) to deeply understand (someone or something)”) +‎ -able (suffix forming adjectives denoting things not able or fit to be done).^[1]

• (Received Pronunciation) IPA^(key): /(ˌ)ʌnˈfæðəməbl̩/, /ʌnˈfæðm̩əbl̩/

• Audio (Southern England):

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• (General American) IPA^(key): /ˌʌnˈfæð(ə)məb(ə)l/
• Hyphenation: un‧fa‧thom‧a‧ble

unfathomable (comparative more unfathomable, superlative most unfathomable)

1. Impossible to fathom.
   1. Especially of depth: physically incapable of being measured; immeasurable.

      Synonyms: (archaic) abyssal, incalculable, inestimable, soundless, unplumbable, unsoundable

      Antonyms: calculable, estimable, fathomable, measurable, plumbable, soundable

      • a. 1677 (date written), Matthew Hale, “A Fifth Consideration Concerning the Decays especially of the Humane Nature, and whether there be any such Decays; and what may be Collected Concerning the Origination of Man upon that Supposition”, in The Primitive Origination of Mankind, Considered and Examined According to the Light of Nature, London: […] William Godbid, for William Shrowsbery, […], published 1677, →OCLC, section II, page 187:

        [W]e are not to make our eſtimate of the quantity of VVaters meerly by the Superficies of the Sea, but by its vaſt depth, vvhich in ſome places is unfathomable, and by thoſe vaſt ſubterraneous Receptacles of VVater vvhich pour themſelves out in ſeveral great Ebullitions and Marine Springs: […]

      • 1712 July 13 (Gregorian calendar), [Joseph Addison], “WEDNESDAY, July 2, 1712. Paper X. On the Pleasures of the Imagination.”, in The Spectator, number 420; republished in Alexander Chalmers, editor, The Spectator; a New Edition, […], volume V, New York, N.Y.: D[aniel] Appleton & Company, 1853, →OCLC, page 79:

        But if we yet rise higher, and consider the fixed stars as so many vast oceans of flame, that are each of them attended with a different set of planets, and still discover new firmaments and new lights, that are sunk farther in those unfathomable depths of ether, so as not to be seen by the strongest of our telescopes, we are lost in such a labyrinth of suns and worlds, and confounded with the immensity and magnificence of nature.

        The spelling has been modernized.

      • 1815 September 10 – December 14, Percy Bysshe Shelley, “Alastor; or, The Spirit of Solitude”, in Alastor; or, The Spirit of Solitude: And Other Poems, London: […] Baldwin, Cradock, and Joy, […]; and Carpenter and Son, […] [b]y S[amuel] Hamilton, […], published 1816, →OCLC, page 26:

        Now, where the fiercest war among the waves / Is calm, on the unfathomable stream / The boat moved slowly.

      • 1851, Elizabeth Barrett Browning, Casa Guidi Windows. A Poem, London: Chapman & Hall, […], →OCLC, part I, stanza XIX, page 52:

        [Y]e may well look up surprised / To those unfathomable heavens that feed / Your purple hills!

      • [1879], [Mary Elizabeth Braddon], “La Chicot”, in The Cloven Foot […], volume I, London: John and Robert Maxwell […], →OCLC, page 71:

        Not till her nineteenth year had she seen the long, dazzling boulevards stretching into unfathomable distance before her eyes; […]

   2. (figurative) Impossible to grasp the extent of, or to fully know or understand.

      Synonyms: bottomless, fathomless, impenetrable, unintelligible; see also Thesaurus:incomprehensible

      Antonyms: explicable, fathomable, intelligible, penetrable, understandable; see also Thesaurus:comprehensible

      The sheer number of warriors the enemy attacked with was unfathomable.

      • 1640, Jos: Exon. [i.e., Joseph Hall], “§. VII. The Fourth Rule of Moderation; to Rest in Those Fundamentall Truthes which are Revealed Clearely in the Scriptures.”, in Christian Moderation. […], London: […] Miles Flesher [and Richard Oulton?], and are to be sold by Nathaniel Butter, →OCLC, 2nd book (Of Moderation in Matter of Iudgement), page 47:

        There are indeed unfadomable depths in that Ocean [i.e., the holy scriptures], vvherin vve ſhall vainly hope to pitch our anchor; but all neceſſary truthes need not much line: […]

      • 1711 March 6 (Gregorian calendar), [Joseph Addison], “FRIDAY, February 23, 1710–1711”, in The Spectator, number 309; republished in Alexander Chalmers, editor, The Spectator; a New Edition, […], volume IV, New York, N.Y.: D[aniel] Appleton & Company, 1853, →OCLC, page 42:

        Their music is employed in celebrating their own criminal exploits, and their discourse in sounding the unfathomable depths of fate, freewill, and foreknowledge.

        The spelling has been modernized.

      • 1719 March 18 (first performance; Gregorian calendar), Edward Young, Busiris, King of Egypt. A Tragedy. […], London: […] J[acob] Tonson, […], published 1719, →OCLC, Act V, page 61:

        Juſt the Blovv, and juſter ſtill, / Becauſe imbitter'd to me by that Hand / I moſt deteſt; vvhich gives my Soul an Earneſt / Of vaſt unfathomable VVoes to come, / That dreadful Dovv'ry for my dreadful Love.

      • 1739, John Wesley, Charles Wesley, “God’s Greatness. From the Same [German].”, in Hymns and Sacred Poems, London: […] William Strahan; and sold by James Hutton, […]; and at Mr. Bray’s, […], →OCLC, part II, stanza I, page 161:

        [W]hat VVords ſuffice / Thy countleſs Attributes to ſhovv: / Unfathomable Depths Thou [God] art!

      • 1817 December (indicated as 1818), Percy B[ysshe] Shelley, “Canto Sixth”, in Laon and Cythna; or, The Revolution of the Golden City: A Vision of the Nineteenth Century. […], London: […] [F]or Sherwood, Neely, & Jones, […]; and C[harles] and J[ames] Ollier, […]; by B[uchanan] M‘Millan, […], →OCLC, stanza XXXVIII, page 147:

        And the sweet peace of joy did almost fill / The depth of her unfathomable look;— […]

      • 1831, Thomas Carlyle, “Centre of Indifference”, in Sartor Resartus: The Life and Opinions of Herr Teufelsdröckh. […], London: Chapman and Hall, […], →OCLC, 2nd book, page 125:

        With respect to Duels, indeed, I have my own ideas. […] Two little visual Spectra of men, hovering with insecure enough cohesion in the midst of the Unfathomable, and to dissolve therein, at any rate, very soon,— […]

        A noun use.

      • 1848 November – 1850 December, William Makepeace Thackeray, “Mrs. Haller”, in The History of Pendennis. […], volume I, London: Bradbury and Evans, […], published 1849, →OCLC, page 36:

        Her eyes, when she lifted them up to gaze on you, and ere she dropped their purple deep-fringed lids, shone with tenderness and mystery unfathomable.

      • 1851, Thomas Babington Macaulay, chapter XXI, in The History of England from the Accession of James the Second, volume IV, London: Longman, Brown, Green, and Longmans, →OCLC, page 575:

        In truth the depths of this man's [John Campbell, 1st Earl of Breadalbane and Holland's] knavery were unfathomable.

      • 1854, Arthur Pendennis [pseudonym; William Makepeace Thackeray], “A Retreat”, in The Newcomes: Memoirs of a Most Respectable Family, volume I, London: Bradbury and Evans, […], →OCLC, page 297:

        Her bushy eyebrows were groves of mystery, her unfathomable eyes were wells of gloom.

      • 1859, George Eliot [pseudonym; Mary Ann Evans], “After the Preaching”, in Adam Bede […], volume I, Edinburgh; London: William Blackwood and Sons, →OCLC, book first, page 62:

        Our caresses, our tender words, […] all bring with them the consciousness that they are mere waves and ripples in an unfathomable ocean of love and beauty: […]

      • 1882, Ouida [pseudonym; Maria Louise Ramé], chapter VIII, in In Maremma […], volume I, London: Chatto & Windus, […], →OCLC, page 212:

        Her lustrous, unfathomable, star-like eyes looked up into his wild and sombre ones; they did not know one another, but each trusted the other after that one long look.

      • 1891, George Meredith, “In which We See a Conventional Gentleman Endeavouring to Examine a Spectre of Himself”, in One of Our Conquerors. […], volume II, London: Chapman and Hall, →OCLC, page 275:

        Lady Cantor spoke to her of Dudley's unfathomable gloom.

      • 2013 April 9, Andrei Lankov, “Stay cool. Call North Korea’s bluff.”, in The New York Times‎^[1], New York, N.Y.: The New York Times Company, →ISSN, →OCLC, archived from the original on 2022-11-11:

        Suggestions that those leaders are irrational and their decisions unfathomable are remarkably shallow. North Korea is not a theocracy led by zealots who preach the rewards of the afterlife.

• unfathomability
• unfathomableness
• unfathomably

• fathom
• fathomable
• fathomless
• unfathomed

• unimaginable
• inconceivable