The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

            I knew a wise man that had it for a byword. --Bacon.
      [1913 Webster]

   2. The object of a contemptuous saying.
      [1913 Webster]

            Thou makest us a byword among the heathen. --Ps.
                                                  xliv. 14
      [1913 Webster]

WordNet (r) 3.0 (2006):

byword
    n 1: a condensed but memorable saying embodying some important
         fact of experience that is taken as true by many people
         [syn: proverb, adage, saw, byword]

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "byword":
   adage, ana, analects, aphorism, apophthegm, apothegm, appellation,
   appellative, axiom, binomen, binomial name, burning shame, butt,
   byname, byword of reproach, catch phrase, catchword, cliche,
   cognomen, collected sayings, cry, cryptonym, current saying,
   denomination, derision, designation, dictate, dictum, dirty shame,
   disgrace, distich, dupe, empty title, epigram, epithet, eponym,
   euonym, expression, fad word, fair game, figure of fun, fool, game,
   gazingstock, gnome, goat, golden saying, handle, honorific,
   humiliation, hyponym, jest, jestingstock, joke, label,
   laughingstock, low-down dirty shame, maxim, mockery, moniker,
   monkey, moral, mot, motto, name, namesake, nomen, nomen nudum,
   oracle, parable, pet expression, phrase, pithy saying, precept,
   prescript, proper name, proper noun, proverb, proverbial saying,
   proverbs, reproach, saw, saying, scandal, scientific name,
   secret name, sentence, sententious expression, shame, shibboleth,
   slogan, sloka, sobriquet, stock, stock saying, style, sutra, tag,
   target, tautonym, teaching, text, title, toy, trinomen,
   trinomial name, verse, victim, vogue word, watchword, wisdom,
   wisdom literature, wise saying, witticism, word, words of wisdom



Easton's 1897 Bible Dictionary:

By-word
   Hebrew _millah_ (Job 30:9), a word or speech, and hence object
   of talk; Hebrew _mashal_ (Ps. 44:14), a proverb or parable. When
   it denotes a sharp word of derision, as in Deut. 28:37, 1 Kings
   9:7, 2 Chr. 7:20, the Hebrew _sheninah_ is used. In Jer. 24:9 it
   is rendered "taunt."