obtuse

Etymology

The OED takes it as borrowed from Latin obtūsus (“blunt, dull, stupid; of an angle, obtuse”),^[2] while Barnhart and the American Heritage Dictionary take it as borrowed from Middle French obtus, feminine obtuse, a learned borrowing from the Latin.^[3][4] The OED compares the French word, recorded for "blunt" from about 1370, in Chauliac; for "stupid" from 1532; and of an angle from 1542.^[2] The Latin adjective is the past participle of obtundō (“to beat against, blunt, dull”),^[2][5][3][6] formed from ob- (“against”) and tundō (“to beat”).^[5][6][7] Etymonline traces it to Proto-Indo-European *(s)teu- (“to push, stick, knock, beat”),^[5] and Klein relates tundō to tudēs (“hammer”).^[8][5] The same verb gave obtund and contusion.^[6][2]

Earliest recorded meaning

Not sharp or pointed, blunt: perhaps before 1425, in a translation of Guy de Chauliac's Grande Chirurgie,^[2][3] and early 15th century in Etymonline.^[5] Dictionary.com dates the word 1500–10.^[9]

Semantic evolution

Ayto explains that the idea of being dulled or blunted led to the sense "dull-witted, stupid", and that bluntness also lies behind the geometrical use for an angle of more than 90 degrees, as against the sharp acute angle.^[6] The figurative sense "slow to understand, insensitive" is recorded from 1509, in Hawes's Pastime of Pleasure,^[2][3] and the geometrical sense from 1570, in Billingsley's translation of Euclid.^[2][5] Weekley compares the parallel figurative senses of acute.^[10] From 1620 to the late 19th century it also meant indistinctly felt or perceived, dull, as of a pain or sound;^[2] Johnson (1755) gave "not shrill; obscure" as of a sound.^[11] The literal sense survives chiefly in botany and zoology.^[2][12]

Timeline

• before 1425 – not sharp or pointed, blunt.^[2][3]
• c. 1487 – verb, to blunt or dull (now obsolete).^[2]
• 1509 – slow to understand, stupid, insensitive.^[2][3]
• 1570 – in geometry, of an angle greater than 90 and less than 180 degrees.^[2]
• 1620 – indistinctly felt or perceived, dull (obsolete by 1897).^[2]

Meanings

Adjective

1. Slow to understand or perceive; lacking sensitivity; dense: He was too obtuse to notice that the guests wanted to leave.^[13][14][2]
2. (mathematics) Of an angle, greater than a right angle and less than 180 degrees; of a triangle, having such an angle.^[14][2]
3. Not sharp or pointed; blunt.^[14][2]
4. Of a leaf or similar part, rounded or blunt at the tip.^[14][2]
5. Indistinctly felt or heard; dull: an obtuse ache.^[14][11]

Word family

• obtusely
• obtuseness
• subobtuse
• obtuse triangle
• obtuse angle

Related words

• obtund
• contusion
• acute
• abstruse

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p q r Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
4. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
5. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ a b c d Ayto, John (2005), Word Origins: The Secret Histories of English Words from A to Z, 2nd ed., London: A & C Black
7. ^ Skeat, Walter W. (1911), A Concise Etymological Dictionary of the English Language, new ed., Oxford: Clarendon Press
8. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
9. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
10. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
11. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
12. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
13. ^ Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
14. ^ a b c d e Collins English Dictionary (2023), Glasgow: HarperCollins