The Collaborative International Dictionary of English v.0.48:

Indiscretion \In`dis*cre"tion\, n. [Pref. in- not + discretion:
   cf. F. indiscr['e]tion.]
   [1913 Webster]
   1. The quality or state of being indiscreet; lack of
      discretion; imprudence.
      [1913 Webster]

   2. An indiscreet act; indiscreet behavior.
      [1913 Webster]

            Past indiscretion is a venial crime.  --Cowper.
      [1913 Webster]

WordNet (r) 3.0 (2006):

indiscretion
    n 1: the trait of being injudicious [syn: indiscretion,
         injudiciousness]
    2: a petty misdeed [syn: indiscretion, peccadillo]

Moby Thesaurus II by Grady Ward, 1.0:

174 Moby Thesaurus words for "indiscretion":
   absurdity, act of folly, atrocity, audacity, babbling, betrayal,
   blabbering, blabbing, bloomer, blunder, boldness, boner, botch,
   brashness, brass, brazen boldness, breach, bungle, callowness,
   carelessness, casualness, cheek, childishness, chutzpah,
   communication leak, crime, crime against humanity,
   crudity of intellect, dead giveaway, deadly sin, delinquency,
   dereliction, divulgation, divulgement, divulgence, divulging,
   dumb trick, enormity, error, evil, evulgation, failure, fault,
   faux pas, felony, folly, foolhardiness, foolishness, gaffe, gall,
   genocide, giveaway, guilty act, haste, hastiness, heavy sin,
   heedlessness, heroics, hubris, immaturity, impetuosity,
   impetuousness, impropriety, improvidence, imprudence, impudence,
   impulsiveness, inadvisability, inappropriateness, inattention,
   inconsideration, indecency, indecorousness, indecorum, indelicacy,
   indiscreetness, indiscriminateness, indiscrimination, inelegance,
   inelegancy, inexpedience, inexpiable sin, iniquity,
   injudiciousness, injury, injustice, insensibility, insensitivity,
   insolence, irrationality, lack of feeling, lack of refinement,
   lapse, leak, letting out, malefaction, malfeasance, malum,
   minor wrong, misdeed, misdemeanor, misfeasance, misstep, mistake,
   mortal sin, naivety, nonfeasance, obvious clue, offense, omission,
   outrage, overboldness, overcarelessness, overconfidence,
   oversureness, overweeningness, peccadillo, peccancy, pompousness,
   promiscuity, promiscuousness, puerility, rashness, reasonlessness,
   recklessness, senselessness, sin, sin of commission,
   sin of omission, sinful act, slip, solecism, sottise, stuffiness,
   stupid thing, stupidity, syncretism, tactlessness, telltale,
   telltale sign, temerariousness, temerity, thoughtlessness, tort,
   transgression, trespass, trip, unchariness, unchastity,
   uncriticalness, undiscriminatingness, undiscriminativeness,
   unfastidiousness, unintelligence, unmeticulousness,
   unparticularness, unpreciseness, unreason, unreasonableness,
   unseemliness, unselectiveness, unsensibleness, unsoundness,
   untactfulness, unthoughtfulness, unutterable sin, unwariness,
   unwisdom, unwise step, unwiseness, unwitting disclosure,
   venial sin, witlessness, wrong



The Devil's Dictionary (1881-1906):

INDISCRETION, n.  The guilt of woman.