The Collaborative International Dictionary of English v.0.48:

Ingenuity \In`ge*nu"i*ty\, n. [L. ingenuitas ingenuousness: cf.
   F. ing['e]nuit['e]. See Ingenuous.]
   1. The quality or power of ready invention; quickness or
      acuteness in forming new combinations; ingeniousness;
      skill in devising or combining.
      [1913 Webster]

            All the means which human ingenuity has contrived.
                                                  --Blair.
      [1913 Webster]

   2. Curiousness, or cleverness in design or contrivance; as,
      the ingenuity of a plan, or of mechanism.
      [1913 Webster]

            He gives . . .
            To artist ingenuity and skill.        --Cowper.
      [1913 Webster]

   3. Openness of heart; ingenuousness. [Obs.]
      [1913 Webster]

            The stings and remorses of natural ingenuity, a
            principle that men scarcely ever shake off, as long
            as they carry anything of human nature about them.
                                                  --South.

   Syn: Inventiveness; ingeniousness; skill; cunning;
        cleverness; genius.

   Usage: Ingenuity, Cleverness. Ingenuity is a form of
          genius, and cleverness of talent. The former implies
          invention, the letter a peculiar dexterity and
          readiness of execution. Sir James Mackintosh remarks
          that the English overdo in the use of the word clever
          and cleverness, applying them loosely to almost every
          form of intellectual ability.
          [1913 Webster]

WordNet (r) 3.0 (2006):

ingenuity
    n 1: the power of creative imagination [syn: inventiveness,
         ingeniousness, ingenuity, cleverness]
    2: the property of being ingenious; "a plot of great ingenuity";
       "the cleverness of its design" [syn: ingenuity,
       ingeniousness, cleverness]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "ingenuity":
   ability, acuteness, address, adeptness, adroitness, airmanship,
   aptness, art, artfulness, artisanship, artistry, bravura,
   brilliance, canniness, capability, capacity, cleverness, command,
   competence, control, coordination, craft, craftsmanship,
   creativeness, creativity, cunning, deftness, dexterity,
   dexterousness, dextrousness, diplomacy, efficiency, expertise,
   facility, faculty, fecundity, fertile mind, fertility, finesse,
   flair, genius, gift, grace, grip, handiness, horsemanship,
   imagination, imaginativeness, ingeniousness, invention,
   inventiveness, keenness, knack, know-how, marksmanship, mastership,
   mastery, originality, practical ability, pregnant imagination,
   productivity, proficiency, prolificacy, prowess, quickness,
   readiness, resource, resourcefulness, savoir-faire, savvy,
   seamanship, sharpness, shrewdness, skill, skillfulness, smartness,
   style, tact, tactfulness, talent, technical brilliance,
   technical mastery, technical skill, technique, teeming imagination,
   timing, virtuosity, wit, wizardry, workmanship