The Collaborative International Dictionary of English v.0.48:

Foolery \Fool"er*y\, n.; pl. Fooleries.
   1. The practice of folly; the behavior of a fool; foolish
      behavior; absurdity.
      [1913 Webster]

            Folly in fools bears not so strong a note,
            As foolery in the wise, when wit doth dote. --Shak.
      [1913 Webster]

   2. An act of folly or weakness; a foolish practice; something
      absurd or nonsensical.
      [1913 Webster]

            That Pythagoras, Plato, or Orpheus, believed in any
            of these fooleries, it can not be suspected. --Sir
                                                  W. Raleigh.
      [1913 Webster]

WordNet (r) 3.0 (2006):

foolery
    n 1: foolish or senseless behavior [syn: folly, foolery,
         tomfoolery, craziness, lunacy, indulgence]

Moby Thesaurus II by Grady Ward, 1.0:

85 Moby Thesaurus words for "foolery":
   Parthian shot, asininity, back answer, banter, battiness,
   brainlessness, buffoonery, caustic remark, clownishness, comeback,
   crack, crackpottedness, crankiness, craziness, cut, cutting remark,
   daffiness, desipience, dig, dump, eccentricity, fatuity,
   fatuousness, fleer, flout, folly, foolheadedness, fooling,
   foolishness, frivolity, frivolousness, gibe, gibing retort,
   giddiness, goofiness, harlequinade, horseplay, idiocy, imbecility,
   inanity, ineptitude, insanity, jab, jape, jeer, jest, leg-pull,
   lunacy, madness, mindlessness, mock, monkeyshines, niaiserie,
   nugacity, nuttiness, parting shot, put-down, put-on, queerness,
   quip, rude reproach, sappiness, scoff, screwiness, scurrility,
   senselessness, shenanigans, short answer, silliness, slam, slap,
   stupidity, swipe, taunt, thoughtlessness, tomfoolery, triflingness,
   triviality, twit, verbal thrust, wackiness, weirdness, witlessness,
   zaniness, zanyism