Source : Webster's Revised Unabridged Dictionary (1913)

Byword \By"word`\, n. [AS. b["i]word; b["i], E. by + word.]
   1. A common saying; a proverb; a saying that has a general
      currency.

            I knew a wise man that had it for a byword. --Bacon.

   2. The object of a contemptuous saying.

            Thou makest us a byword among the heathen. --Ps.
                                                  xliv. 14

Source : WordNet®

byword
     n : a condensed but memorable saying embodying some important
         fact of experience that is taken as true by many people
         [syn: {proverb}, {adage}, {saw}]