Source : Webster's Revised Unabridged Dictionary (1913)

By-blow \By"-blow`\, n.
   1. A side or incidental blow; an accidental blow.

            With their by-blows they did split the very stones
            in pieces.                            --Bunyan.

   2. An illegitimate child; a bastard.

            The Aga speedily . . . brought her [his disgraced
            slave] to court, together with her pretty by-blow,
            the present Padre Ottomano.           --Evelyn.

Source : WordNet®

by-blow
     n : the illegitimate offspring of unmarried parents [syn: {bastard},
          {love child}, {illegitimate child}, {illegitimate}, {whoreson}]