The Collaborative International Dictionary of English v.0.48:

Nostrum \Nos"trum\ (-tr[u^]m), n.; pl. Nostrums (-tr[u^]mz).
   [Neut. sing. of L. noster ours, fr. nos we. See Us.]
   [1913 Webster]
   1. A medicine, the ingredients of which are kept secret for
      the purpose of restricting the profits of sale to the
      inventor or proprietor; a quack medicine.
      [1913 Webster]

   2. Any scheme or device proposed by a quack.
      [1913 Webster]

            The incentives of agitators, the arts of impostors
            and the nostrums of quacks.           --Brougham.
      [1913 Webster]

   3. Any scheme asserted to solve a problem, but with no
      objective basis for belief in its effectiveness; esp., in
      politics, a scheme or proposal likely to prove popular
      with voters.
      [PJC]

WordNet (r) 3.0 (2006):

nostrum
    n 1: hypothetical remedy for all ills or diseases; once sought
         by the alchemists [syn: panacea, nostrum, catholicon,
         cure-all]
    2: patent medicine whose efficacy is questionable