The Collaborative International Dictionary of English v.0.48:

Balderdash \Bal"der*dash\, n. [Of uncertain origin: cf. Dan.
   balder noise, clatter, and E. dash; hence, perhaps, unmeaning
   noise, then hodgepodge, mixture; or W. baldorduss a
   prattling, baldordd, baldorddi, to prattle.]
   1. A worthless mixture, especially of liquors.
      [1913 Webster]

            Indeed beer, by a mixture of wine, hath lost both
            name and nature, and is called balderdash. --Taylor
                                                  (Drink and
                                                  Welcome).
      [1913 Webster]

   2. Senseless jargon; ribaldry; nonsense; trash.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Balderdash \Bal"der*dash\, v. t.
   To mix or adulterate, as liquors.
   [1913 Webster]

         The wine merchants of Nice brew and balderdash, and
         even
         mix it with pigeon's dung and quicklime. --Smollett.
   [1913 Webster]

WordNet (r) 3.0 (2006):

balderdash
    n 1: trivial nonsense [syn: balderdash, fiddle-faddle,
         piffle]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "balderdash":
   absurdity, amphigory, babble, babblement, bibble-babble, bilge,
   blabber, blather, bombast, bombastry, bosh, bushwa, claptrap,
   double-talk, drivel, drool, eyewash, fiddle-faddle, fiddledeedee,
   flummery, folderol, fudge, fustian, gabble, galimatias, gammon,
   gibber, gibberish, gibble-gabble, gobbledygook, highfalutin,
   hocus-pocus, hot air, humbug, jabber, jargon, malarkey,
   mumbo jumbo, narrishkeit, niaiserie, nonsense, pack of nonsense,
   palaver, prate, prattle, rant, rigamarole, rigmarole, rodomontade,
   rot, rubbish, skimble-skamble, stuff and nonsense, stultiloquence,
   trash, trumpery, twaddle, twattle, twiddle-twaddle, vaporing,
   waffling