- careless, reckless, not exercising proper caution
1749, Henry Fielding, chapter XV, in The History of Tom Jones, a Foundling, London: A[ndrew] Millar, OCLC 928184292, book VIII:
- "You might have remained so still," replies Jones, "if you had not been unfortunate, I will venture to say incautious, in the placing your affections.
- 1912, Stratemeyer Syndicate, Baseball Joe on the School Nine Chapter 1
- "Yes, let 'Sister' Davis have a whack at it too," urged George Bland. Tom Davis, who was Joe Matson's particular chum, was designated "Sister" because, in an incautious moment, when first coming to Excelsior Hall, he had shown a picture of his very pretty sister, Mabel.