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The angle marked β is obtuse (sense 4) as it is greater than 90° but less than 180°

From Middle French obtus (obtuse (geometry); narrow-minded, obtuse; boring, dull, lifeless), from Latin obtūsus (blunt, dull; obtuse), past participle of obtundere, from obtundō (to batter, beat, strike; to blunt, dull), from ob- (prefix meaning against) + tundō (to beat, strike; to bruise, crush, pound) (ultimately from Proto-Indo-European *(s)tewd-, from *(s)tew- (to hit; to push)).



obtuse (comparative obtuser or more obtuse, superlative obtusest or most obtuse)

  1. Intellectually dull or dim-witted.
    • 1613, [Robert Anton], Moriomachia[1], imprinted at London: By Simon Stafford, OCLC 800723901, archived from the original on 14 January 2018:
      It was a merry time with Carrmen, Watermen, & Porters: for in this Eclipſe, many of them did nothing but drinke, domineere, and ſwagger in Alehouſes; but the often going to and fro of the Pot, made them talke of that, which they had nothing to doe withall, and many times their obtuſe apprehenſions would be medling with the warres betwixt the great Turke and Preſter Iohn, how it was likely to end; []
    • 1848, William Makepeace Thackeray, Vanity Fair, Chapter 21:
      When the elder Osborne gave what he called "a hint," there was no possibility for the most obtuse to mistake his meaning. He called kicking a footman downstairs a hint to the latter to leave his service.
    • 2017 March 27, “The Observer view on triggering article 50: As Britain hurtles towards the precipice, truth and democracy are in short supply [editorial]”, in The Observer[2], London, archived from the original on 30 August 2017:
      Be you a Remainer or a Leaver, you would have to be particularly obtuse not to see that [Theresa] May's hard Tory Brexit will cost this country and its families more than it can conceivably afford.
  2. Indirect or circuitous.
  3. Of sound, etc.: deadened, muffled, muted.
    • 1661, Robert Lovell, “Dynamilogia Pharmaceutica. Or The Whole Use, of All Simples and Compounds Contained in the London Dispensatory, with the Diseases Cured by Them in Alphabetical Order: Together with the Doses and Formes of All Kinds of Remedies.”, in ΠΑΝΖΩΟΡΥΚΤΟΛΟΓΙΑ [PANZŌORYKTOLOGIA]. Sive Panzoologicomineralogia. Or a Compleat History of Animals and Minerals, Containing the Summe of All Authors, both Ancient and Modern, Galenicall and Chymicall, [...], Oxford: Printed by Hen[ry] Hall, for Jos[eph] Godwin, OCLC 79920846, page 517:
      The ſenſe of the inteſtines, if exquiſite, wants a more gentle remedie; and if dull, a ſtronger: Alſo the ſenſes of the inteſtines are perceived by the courſe of diet; for thoſe that feed upon muſtard, or the like biting and more ſharp meat, without trouble, are of a more obtuſe ſenſe; but thoſe of an exact ſenſe, which preſently perceive the mordacity; and thoſe that are of a mean ſenſe, want a mean doſe.
    • 1847 January, “Art. VI.—A Universal and Critical Dictionary of the English Language; to which are added Walker’s Key to the Pronunciation of Classical and Scripture Proper Names, much enlarged and improved; and a Pronouncing Vocabulary of Modern Geographical Names. By Joseph E. Worcester. Boston: Wilkins, Carter, & Co. Imperial 8vo. pp. 955. [book review]”, in The North American Review, volume LXIV, number CXXXIV, Boston, Mass.: Published by Otis, Broaders, and Co., No. 154 Washington Street, OCLC 956094611, page 198:
      Another addition in Mr. [Joseph Emerson] Worcester's key to the same letter [e] is what he calls the short and obtuse sound, as in her, herd, fern, fervid. Some of these, also, for the sake of indicating the true sound, [John] Walker was obliged to spell with a different vowel. Thus her is directed to be pronounced hur, like u in tub.
  4. (geometry) Of an angle: greater than 90 degrees but less than 180 degrees.
    • 1623, Charles Butler, “Of the Hiues, and the Dreſsing of Them”, in The Feminine Monarchie: Or The Historie of Bees. Shewing Their Admirable Nature, and Properties, Their Generation, and Colonies, Their Gouernment, Loyaltie, Art, Industrie, Enemies, Warres, Magnanimitie, &c. Together with the Right ordering of Them from Time to Time: And the Sweet Profit Arising thereof. Written out of Experience, London: Printed by Iohn Haviland for Roger Iackson, and are to be sold at his Shop in Fleetstreet, ouer against the Conduit, OCLC 63334619, footnote c:
      If you put foure Spleets in a Hiue, then cut their backes, where they muſt leane one againſt another, to ſquare angles, ſuch as be foure in a circle: if but three, cut them to obtuſe angles, ſuch as are three in a circle: (you may readily try them, before you put them in, by Moulds made iuſt to thoſe formes) and ſo will they ſtand cloſe and firme together.
    • 1877, Ch[arles] Couche; James N. Shoolbred, transl., “Special Points in the Permanent Way”, in Permanent Way Rolling Stock and Technical Working of Railways. Followed by an Appendix on Works of Art, volume I, London: Dulau & Co., 37, Soho Square; Paris: Dunod, 49, Quai des Augustins, OCLC 58932800, § XIV (Rail-crossings), paragraph 258, page 316:
      Obtuse angles of the through crossing. — The system of the two obtuse-angled points is especially termed the dead-crossing. [] The point itself, less liable to damage than that of the crossing proper, on account of its obtuse form and its position relatively to the wheels, acts the same part towards the tapered portion of the cut rail, as the wing-rail does with respect to the acute-angle of the crossing.
    • 1922, May Sinclair, “Space, Time and Other Consciousnesses”, in The New Idealism, New York, N.Y.: The Macmillan Company, OCLC 558287, section v, pages 255–256:
      If he is standing close beside me I know that our separate axes of vision will meet at an acute angle in the centre of his object, and if we are further apart, at an obtuser angle.
  5. (geometry) Of a triangle: having one obtuse angle.
    • 2013, Edward J. Barbeau, “Probability and Statistics”, in More Fallacies, Flaws, and Flimflam (Spectrum Series), Washington, D.C.: Mathematical Association of America, →ISBN, page 128:
      Ruma Falk wrote an article entitled Lewis Carroll's obtuse problem, published in Teaching statistics 23:3 (Autumn, 2001), 72–75. She discussed the Pillow Problem No. 58 from the collection published in 1895 by Lewis Carroll: / Three points are taken at random on an infinite Plane. Find the chance of their being the vertices of an obtuse-angled Triangle. / [] Then the third vertex of the triangle cannot fall outside of the figure  . If it falls inside the semi-circle, then the triangle is obtuse, []
  6. (now chiefly botany, zoology) Not sharp; blunt.



Derived termsEdit

Related termsEdit



obtuse (third-person singular simple present obtuses, present participle obtusing, simple past and past participle obtused)

  1. (transitive, obsolete) To dull or reduce an emotion or a physical state.
    • 1611, Randle Cotgrave, comp., “Fouler”, in A Dictionarie of the French and English Tongves, London: Printed by Adam Islip, OCLC 491770318, column 2:
      Fouler. To tread, ſtampe, or trample on; to bruiſe, or cruſh, by ſtamping; hurt, or obtuſe, by treading on; []
    • 1861 August, “[Miscellaneous.] Coca”, in The United States Journal of Homœopathy, volume II, New York, N.Y.: C. T. Hurlburt, No. 437 Broome Street, OCLC 64159880, page 549:
      The general effect of even a weak infusion of coca leaves is a pleasant irritability and sleeplessness. A stronger infusion keeps hunger away, prevents loss of breath in ascending mountains, dilates the pupil, and obtuses the sensibility to the air.
    • 1900 July 13, George M. Kober, “Shall Alcohol be Considered as a Food?”, in Landon B. Edwards and Charles M. Edwards, editors, Virginia Medical Semi-monthly (Richmond), volume V, number 7 (103 overall), Richmond, Va.: J. W. Fergusson & Son, printers [for the Medical Society of Virginia], published 1901, OCLC 1769197, page 205, column 1:
      [Gustav von] Bunge [] claims that its [alcohol's] primary action is that of a depressant, and that its apparent good effects are simply due to the obtusing influence upon physical and mental suffering. But this is scarcely a correct assumption, as there are individuals in whom the smallest doses produce palpitation of the heart, throbbing of the carotids, and great mental activity. He also claims that alcohol does not produce renewed vigor in tired individuals, but simply obtuses this feeling of exhaustion.
    • 1916, Henry Goddard Leach, editor, The American-Scandinavian Review, volume 4, New York, N.Y.: The American-Scandinavian Foundation, ISSN 0003-0910, OCLC 6460493, page 51:
      The American avidity for "action" has evidently obtused the perceptions of habitual theatre-goers to all nuances of feeling, and therefore, the harmless romancings of the elderly estranged couple, Mr. and Mrs. Arvik, are interpreted as covering unspeakable iniquities that only exist in the minds of the critics.


Further readingEdit






  1. feminine singular of obtus





  1. vocative masculine singular of obtūsus