different between shallow-brained vs incautious

English

From in- (negative prefix) +? cautious.

incautious (comparative more incautious, superlative most incautious)

careless, reckless, not exercising proper caution.
- 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.
Synonym: uncautious

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