The Collaborative International Dictionary of English v.0.48:

Proverbial \Pro*ver"bi*al\, a. [L. proverbialis: cf. F.
   proverbial.]
   1. Mentioned or comprised in a proverb; used as a proverb;
      hence, commonly known; as, a proverbial expression; his
      meanness was proverbial.
      [1913 Webster]

            In case of excesses, I take the German proverbial
            cure, by a hair of the same beast, to be the worst.
                                                  --Sir W.
                                                  Temple.
      [1913 Webster]

   2. Of or pertaining to proverbs; resembling a proverb. "A
      proverbial obscurity." --Sir T. Browne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

proverbial
    adj 1: of or relating to or resembling or expressed in a
           proverb; "he kicked the proverbial bucket"; "the
           proverbial grasshopper"
    2: widely known and spoken of; "her proverbial lateness"; "the
       proverbial absentminded professor"; "your proverbial dizzy
       blonde"

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "proverbial":
   accepted, acknowledged, aphoristic, apophthegmatic, apothegmatic,
   archetypal, axiomatic, common, commonly known, commonplace, crisp,
   current, epigrammatic, exemplary, familiar, formulaic, formulistic,
   gnomic, hackneyed, homiletic, household, moralistic, notorious,
   pithy, platitudinous, pointed, public, pungent, sententious,
   succinct, talked-about, talked-of, terse, time-honored,
   traditional, trite, truistic, typical, universally admitted,
   universally recognized, well-kenned, well-known, well-recognized,
   well-understood, widely known