indefensible

Etymology

It is formed from English in- + defensible, the prefix meaning "not".^{[2][3][4][5][6]} Defensible is from Old French defensable, from Medieval Latin defensibilis, from the past participle stem of Latin dēfendō (“to defend”).^[3] The OED compares French indéfensible, used by Montaigne in the 16th century.^[2]

Earliest recorded meaning

That cannot be defended in argument or justified; inexcusable: 1529, in T. More's Dialogue Heresyes.^[2][5] Etymonline dates it to the 1520s.^[3]

Semantic evolution

The sense "that cannot be defended by force of arms" followed in 1569, in T. Stocker's translation of Diodorus Siculus;^[2] Etymonline dates it to the 1560s.^[3] Johnson (1755) defined the word as "what cannot be defended or maintained", quoting Sanderson.^[7] Both senses are still current: the word is used of arguments and positions that cannot be upheld, of conduct that cannot be excused, and of places that cannot be held against attack.^[5][8]

Timeline

• 1529 – that cannot be maintained in argument or justified; inexcusable.^[2][5] Etymonline dates it to the 1520s.^[3]
• 1569 – that cannot be defended by force of arms.^[2] Etymonline dates this sense to the 1560s.^[3]

Meanings

Adjective

1. Impossible to justify or excuse: Leaving the dog shut in the car all afternoon was indefensible.^[8][5][2]
2. That cannot be maintained as valid in argument; untenable.^[8][5]
3. That cannot be defended against attack, especially by armed force.^[8][5][2]

Word family

• indefensibility
• indefensibly

Related words

• defensible
• defend

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
6. ^ Gove, Philip Babcock, ed. (1961), Webster's Third New International Dictionary of the English Language, Unabridged, Springfield, Mass.: G. & C. Merriam
7. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
8. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins