[1] : The Collaborative International Dictionary of English v.0.48

foolishness \fool"ishness\, n.
   1. the quality of being foolish.
      1913 webster

   2. a foolish practice; an absurdity.
      1913 webster

            the preaching of the cross is to them that perish
            foolishness.                          --1 cor. i.
                                                  18.
      1913 webster

[2] : WordNet (r) 2.0

foolishness
     n 1: the trait of acting stupidly or rashly syn: folly, unwiseness
          ant: wisdom
     2: the quality of being rash and foolish syn: folly, craziness
     3: a stupid mistake syn: stupidity, betise, folly, imbecility
see also:
folly unwiseness wisdom craziness stupidity betise 
imbecility 

[3] : Moby Thesaurus II by Grady Ward, 1.0

105 moby thesaurus words for "foolishness":
   urdummheit, absurdity, absurdness, big deal, blank mind,
   blankmindedness, blankness, brainlessness, bull, bunk,
   calm of mind, craziness, devilishness, devilment, devilry,
   deviltry, dottiness, elfishness, emptiness, emptiness of mind,
   empty-headedness, fallow mind, fatuity, flightiness, flimsiness,
   folly, frivolity, frivolousness, futility, giddiness, high spirits,
   idleness, ignorance, impishness, impracticality, imprudence,
   inanity, incapacity, indiscretion, ineptitude, injudiciousness,
   insanity, insensibility, irrationality, lackbrainedness,
   lackwittedness, levity, lightness, low iq, ludicrousness, lunacy,
   mental blankness, mental weakness, mercuriality, mindlessness,
   mischief, mischievousness, nirvana, nonsense, nugacity, oblivion,
   passivity, playfulness, prankishness, pranksomeness,
   preposterousness, primal stupidity, puckishness, quietism,
   reasonlessness, ridiculousness, roguery, roguishness, scampishness,
   senselessness, shallowness, silliness, slackmindedness,
   slackwittedness, slenderness, slightness, sportiveness,
   superficiality, tabula rasa, thoughtfreeness, thoughtlessness,
   tranquillity, triflingness, triteness, triviality, trivialness,
   unintellectuality, unintelligence, unreasonableness, unwisdom,
   unwiseness, vacancy, vacuity, vanity, vapidity, volatility,
   waggery, waggishness, witlessness, youthful spirits

Foolishness >> F Words
Foolishness, definition of term: Foolishness
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