Definition of "by-blow" in English

noun

1. A blow struck to the side or from the side, as in swordplay; a secondary or incidental strike of any sort.

2. (slang) An illegitimate child; a child of an unknown or unmarried father.

   • c. 1892, Herman Melville, "Billy Budd, Foretopman" (novella), in Herman Melville: Selected Tales and Poems, Holt, Rinehart & Winston (1950), p. 298, Yes, Billy was a foundling, a presumable bye-blow, and, evidently, no ignoble one.