The Collaborative International Dictionary of English v.0.48:

Ineptitude \In*ept"i*tude\, n. [L. ineptitudo.]
   [1913 Webster]
   1. The quality of being inept; unfitness; inaptitude;
      unsuitableness.
      [1913 Webster]

            That ineptitude for society, which is frequently the
            fault of us scholars.                 --Tatler.
      [1913 Webster]

   2. Absurdity; nonsense; foolishness.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ineptitude
    n 1: unskillfulness resulting from a lack of training [syn:
         awkwardness, clumsiness, ineptness, ineptitude,
         maladroitness, slowness]
    2: having no qualities that would render it valuable or useful;
       "the drill sergeant's intent was to convince all the recruits
       of their worthlessness" [syn: worthlessness, ineptitude]
       [ant: worth]

Moby Thesaurus II by Grady Ward, 1.0:

113 Moby Thesaurus words for "ineptitude":
   Urdummheit, absurdity, asininity, awkwardness, battiness,
   brainlessness, buffoonery, clownishness, clumsiness,
   crackpottedness, crankiness, craziness, daffiness, desipience,
   disability, disablement, disqualification, eccentricity, fatuity,
   fatuousness, folly, foolery, foolheadedness, foolishness,
   frivolity, frivolousness, futility, gaucherie, giddiness,
   goofiness, idiocy, ignorance, imbecility, impoliticalness,
   impoliticness, inability, inadequacy, inadvisability, inanity,
   inappropriateness, inaptitude, inaptness, incapability,
   incapacitation, incapacity, incompetence, incompetency,
   incongruity, inconvenience, inconveniency, inefficiency, ineptness,
   inexpedience, inexpediency, infancy, infelicity, inferiority,
   inopportuneness, insanity, insufficiency, irrationality,
   lackbrainedness, lackwittedness, legal incapacity, low IQ, lunacy,
   madness, maladroitness, mental weakness, mindlessness, minority,
   niaiserie, nugacity, nuttiness, primal stupidity, queerness,
   reasonlessness, sappiness, screwiness, senselessness, silliness,
   slackmindedness, slackwittedness, stupidity, thoughtlessness,
   triflingness, triviality, undesirability, unfitness, unfittingness,
   unfortunateness, ungainliness, unintellectuality, unintelligence,
   unmeetness, unprofitability, unprofitableness, unseasonableness,
   unseemliness, unsuitability, unsuitableness, untimeliness,
   unwisdom, unwiseness, uselessness, wackiness, wardship, weirdness,
   witlessness, worthlessness, wrongness, zaniness, zanyism