The Collaborative International Dictionary of English v.0.48:

Mischief \Mis"chief\ (m[i^]s"ch[i^]f), n. [OE. meschef bad
   result, OF. meschief; pref. mes- (L. minus less) + chief end,
   head, F. chef chief. See Minus, and Chief.]
   [1913 Webster]
   1. Harm; damage; esp., disarrangement of order; trouble or
      vexation caused by human agency or by some living being,
      intentionally or not; often, calamity, mishap; trivial
      evil caused by thoughtlessness, or in sport. --Chaucer.
      [1913 Webster]

            Thy tongue deviseth mischiefs.        --Ps. lii. 2.
      [1913 Webster]

            The practice whereof shall, I hope, secure me from
            many mischiefs.                       --Fuller.
      [1913 Webster]

   2. Cause of trouble or vexation; trouble. --Milton.
      [1913 Webster]

            The mischief was, these allies would never allow
            that the common enemy was subdued.    --Swift.
      [1913 Webster]

   To be in mischief, to be doing harm or causing annoyance.


   To make mischief, to do mischief, especially by exciting
      quarrels.

   To play the mischief, to cause great harm; to throw into
      confusion. [Colloq.]
      [1913 Webster]

   Syn: Damage; harm; hurt; injury; detriment; evil; ill.

   Usage: Mischief, Damage, Harm. Damage is an injury
          which diminishes the value of a thing; harm is an
          injury which causes trouble or inconvenience; mischief
          is an injury which disturbs the order and consistency
          of things. We often suffer damage or harm from
          accident, but mischief always springs from perversity
          or folly.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mischief \Mis"chief\, v. t.
   To do harm to. [Obs.] --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mischief
    n 1: reckless or malicious behavior that causes discomfort or
         annoyance in others [syn: mischief, mischief-making,
         mischievousness, deviltry, devilry, devilment,
         rascality, roguery, roguishness, shenanigan]
    2: the quality or nature of being harmful or evil [syn:
       maleficence, mischief, balefulness] [ant:
       beneficence]

Moby Thesaurus II by Grady Ward, 1.0:

167 Moby Thesaurus words for "mischief":
   Discordia, Eris, abomination, atrocity, bad, bad boy, badness,
   bane, bankruptcy, befoulment, blight, booger, breakage, breakdown,
   buffoon, bugger, clash, clashing, collapse, conflict, contention,
   corruption, crack-up, crippling, crying evil, cutup, damage,
   defilement, despoliation, destruction, detriment, devil,
   devilishness, devilment, devilry, deviltry, diablerie, difference,
   difficulty, dilapidation, disablement, disaccord, disadvantage,
   disaffinity, discord, discordance, discordancy, disharmony,
   disrepair, disruption, dissension, dissent, division, drawback,
   elf, elfishness, encroachment, enfant terrible, enmity, evil,
   foolishness, friction, funmaker, grievance, handicap, hardship,
   harm, havoc, high spirits, hobbling, hood, hoodlum, hooligan, hurt,
   hurting, ill, imp, impairment, impishness, incapacitation,
   incompatibility, incompatibleness, infection, infringement,
   inharmoniousness, inharmony, injury, inroad, jangle, jar, joker,
   jokester, knave, liability, limb, little devil, little monkey,
   little rascal, loss, loss of ground, maiming, mayhem, minx,
   misbehavior, mischief-maker, mischievousness, misfortune,
   monkey business, monkeyshines, mutilation, naughtiness,
   noncooperation, open conflict, outrage, pixie, playfulness, poison,
   pollution, practical joker, prankishness, pranksomeness, prankster,
   prejudice, puck, puckishness, rapscallion, rascal, rascality,
   rogue, roguery, roguishness, rowdy, rub, ruffian, ruin, ruination,
   ruinousness, sabotage, scalawag, scamp, scampishness, scapegrace,
   scathe, shenanigans, sickening, spoiling, sportiveness,
   step backward, strained relations, strife, tension, the worst,
   toxin, trouble, unharmoniousness, unpleasantness, variance, venom,
   vexation, villain, wag, waggery, waggishness, weakening, woe,
   wrong, youthful spirits