The Collaborative International Dictionary of English v.0.48:

Concoction \Con*coc"tion\, n. [L. concoctio.]
   1. A change in food produced by the organs of nutrition;
      digestion. [Obs.]
      [1913 Webster]

   2. The act of concocting or preparing by combining different
      ingredients; also, the food or compound thus prepared.
      [1913 Webster]

   3. The act of digesting in the mind; planning or devising;
      rumination. --Donne.
      [1913 Webster]

   4. (Med.) Abatement of a morbid process, as a fever and
      return to a normal condition. [Obs.]
      [1913 Webster]

   5. The act of perfecting or maturing. [Obs.] --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

concoction
    n 1: any foodstuff made by combining different ingredients; "he
         volunteered to taste her latest concoction"; "he drank a
         mixture of beer and lemonade" [syn: concoction,
         mixture, intermixture]
    2: an occurrence of an unusual mixture; "it suddenly spewed out
       a thick green concoction"
    3: the invention of a scheme or story to suit some purpose; "his
       testimony was a concoction"; "she has no peer in the
       concoction of mystery stories"
    4: the act of creating something (a medicine or drink or soup
       etc.) by compounding or mixing a variety of components [syn:
       confection, concoction]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "concoction":
   admixture, alloy, amalgam, artifact, authorship, beginning, blend,
   brainchild, brew, canard, child, coinage, combination, combo,
   commixture, composite, conception, confection, contrivance,
   contriving, creation, creative effort, creature,
   crowning achievement, decoction, decoctum, devising, distillation,
   effect, end product, ensemble, essence, extract, extravaganza,
   fable, fabrication, fiction, figment, forgery, fruit, generation,
   handiwork, hatching, immixture, improvisation, intermixture,
   invention, issue, magma, making do, manufacture, masterpiece,
   masterwork, mintage, mixture, myth, new mintage, offspring, opera,
   opus, opuscule, origination, outcome, outgrowth, paste, product,
   production, result, romance, work