The Collaborative International Dictionary of English v.0.48:

Concoct \Con*coct"\, v. t. [imp. & p. p. Concocted; p. pr. &
   vb. n. Concocting.] [L. concoctus, p. p. of concoquere to
   cook together, to digest, mature; con- + coquere to cook. See
   Cook.]
   1. To digest; to convert into nourishment by the organs of
      nutrition. [Obs.]
      [1913 Webster]

            Food is concocted, the heart beats, the blood
            circulates.                           --Cheyne.
      [1913 Webster]

   2. To purify or refine chemically. [Obs.] --Thomson.
      [1913 Webster]

   3. To prepare from crude materials, as food; to invent or
      prepare by combining different ingredients; as, to concoct
      a new dish or beverage.
      [1913 Webster]

   4. To digest in the mind; to devise; to make up; to contrive;
      to plan; to plot.
      [1913 Webster]

            He was a man of a feeble stomach, unable to concoct
            any great fortune.                    --Hayward.
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   5. To mature or perfect; to ripen. [Obs.] --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

concoct
    v 1: make a concoction (of) by mixing
    2: prepare or cook by mixing ingredients; "concoct a strange
       mixture" [syn: concoct, cook up]
    3: invent; "trump up charges" [syn: trump up, concoct]
    4: devise or invent; "He thought up a plan to get rich quickly";
       "no-one had ever thought of such a clever piece of software"
       [syn: think up, think of, dream up, hatch, concoct]

Moby Thesaurus II by Grady Ward, 1.0:

164 Moby Thesaurus words for "concoct":
   accessory, accompanying, adjuvant, admix, alloy, amalgamate,
   ancillary, angle, assemble, attendant, attending, beget, bemingle,
   blend, breed, brew, bring forth, bring into being, build, cabal,
   call into being, cast, coalesce, coin, coincident, collateral,
   collude, combine, commingle, commix, complot, compose, compound,
   conceit, conceive, conceptualize, conglomerate, connive, conspire,
   construct, contrive, cook up, correlative, corresponding,
   counterfeit, countermine, counterplot, create, decoct, design,
   develop, devise, discover, dream up, elaborate, emulsify, engender,
   engineer, envisage, envision, erect, evolve,
   experience imaginatively, extrude, fabricate, fake, fancy,
   fantasize, fashion, fictionalize, finagle, finesse, fix up, forge,
   form, formulate, frame, frame up, fudge, fudge together, fuse,
   generate, get up, give being to, give rise to, hash, hatch,
   hatch a plot, hatch up, hoke up, homogenize, ideate, imagine,
   immingle, immix, improvise, incident, indite, integrate,
   interblend, interlace, interlard, intermingle, intermix,
   intertwine, interweave, intrigue, invent, jumble, knead,
   lay a plot, machinate, make, make do with, make up, maneuver,
   manufacture, mature, merge, mingle, mingle-mangle, mint, mix,
   mix up, mold, operate, origin, originate, patch together,
   piece together, plan, plot, prefabricate, prepare, procreate,
   produce, put together, put up, raise, rear, rig, run up, satellite,
   scheme, scramble, set up, shape, shuffle, spawn, stir up,
   strike out, supplementary, suppose, syncretize, think out,
   think up, throw together, toss together, trump up, vamp up, wangle,
   whomp up, work, write