The Collaborative International Dictionary of English v.0.48:

Complaint \Com*plaint"\ (k[o^]m*pl[=a]nt"), n. [F. complainte.
   See Complain.]
   1. Expression of grief, regret, pain, censure, or resentment;
      lamentation; murmuring; accusation; fault-finding.
      [1913 Webster]

            I poured out my complaint before him. --Ps. cxlii.
                                                  2.
      [1913 Webster]

            Grievous complaints of you.           --Shak.
      [1913 Webster]

   2. Cause or subject of complaint or murmuring.
      [1913 Webster]

            The poverty of the clergy in England hath been the
            complaint of all who wish well to the church.
                                                  --Swift.
      [1913 Webster]

   3. An ailment or disease of the body.
      [1913 Webster]

            One in a complaint of his bowels.     --Arbuthnot.
      [1913 Webster]

   4. (Law) A formal allegation or charge against a party made
      or presented to the appropriate court or officer, as for a
      wrong done or a crime committed (in the latter case,
      generally under oath); an information; accusation; the
      initial bill in proceedings in equity.

   Syn: Lamentation; murmuring; sorrow; grief; disease; illness;
        disorder; malady; ailment.
        [1913 Webster]

WordNet (r) 3.0 (2006):

complaint
    n 1: an often persistent bodily disorder or disease; a cause for
         complaining [syn: ailment, complaint, ill]
    2: (formerly) a loud cry (or repeated cries) of pain or rage or
       sorrow
    3: an expression of grievance or resentment
    4: (civil law) the first pleading of the plaintiff setting out
       the facts on which the claim for relief is based
    5: (criminal law) a pleading describing some wrong or offense;
       "he was arrested on a charge of larceny" [syn: charge,
       complaint]

Moby Thesaurus II by Grady Ward, 1.0:

235 Moby Thesaurus words for "complaint":
   abnormality, accusal, accusation, accusing, acute disease,
   affection, affidavit, affliction, ailment, allegation, allegement,
   allergic disease, allergy, arraignment, atrophy, bacterial disease,
   ban, beef, beefing, bellyache, bellyaching, bill,
   bill of complaint, bill of particulars, birth defect, bitch,
   bitching, blackball, blackballing, blame, blight, boycott,
   bringing of charges, bringing to book, cardiovascular disease,
   challenge, charge, chronic disease, circulatory disease, claim,
   combative reaction, complaining, complication, compunction,
   condition, congenital defect, count, counteraction, declaration,
   defect, defiance, deficiency disease, deformity,
   degenerative disease, delation, demonstration, demur, demurrer,
   denouncement, denunciation, deposition, destructive criticism,
   dim view, disability, disagreement, disappointment, disapprobation,
   disapproval, discontent, discontentedness, discontentment, disease,
   disenchantment, disesteem, disfavor, disgruntlement, disillusion,
   disillusionment, disorder, displeasure, dispute, disrespect,
   dissatisfaction, dissent, dissentience, distaste, distemper,
   endemic, endemic disease, endocrine disease, epidemic disease,
   exception, exclusion, expostulation, faultfinding, fractiousness,
   functional disease, fungus disease, gastrointestinal disease,
   genetic disease, grievance, grievance committee, gripe, griping,
   groan, groaning, grouse, grousing, grumble, grumbling, handicap,
   hereditary disease, holler, howl, iatrogenic disease, ill, illness,
   impeachment, implication, imputation, indictment, indignation,
   indignation meeting, indisposition, infectious disease, infirmity,
   information, innuendo, insinuation, kick, kicking, lawsuit,
   laying of charges, libel, low estimation, low opinion, malady,
   malaise, march, morbidity, morbus, murmuring, muscular disease,
   narratio, negativism, neurological disease, nolle prosequi,
   noncooperation, nonsuit, nonviolent protest, nutritional disease,
   objection, obstinacy, occupational disease, opposition, opposure,
   organic disease, ostracism, pandemic disease, passive resistance,
   pathological condition, pathology, peeve, peevishness, pet peeve,
   petulance, picketing, plaint, plant disease, prosecution, protest,
   protest demonstration, protestation, protozoan disease,
   psychosomatic disease, qualm, querulousness, rally, reaction,
   rebuff, recalcitrance, recalcitrancy, recalcitration,
   refractoriness, rejection, reluctance, remonstrance, remonstration,
   renitence, renitency, repellence, repellency, reproach, repulse,
   repulsion, resistance, respiratory disease, revolt, rockiness,
   scolding, scruple, secondary disease, seediness, sickishness,
   sickness, signs, sit-in, sniping, squawk, squawking, stand,
   statement, statement of facts, strike, suit, symptomatology,
   symptomology, symptoms, syndrome, taxing, teach-in, the pip,
   thumbs-down, true bill, uncooperativeness, unhappiness,
   unspoken accusation, urogenital disease, veiled accusation,
   virus disease, wasting disease, whining, withstanding,
   worm disease, yapping



Bouvier's Law Dictionary, Revised 6th Ed (1856):

COMPLAINT, crim. law. The allegation made to a proper officer, that some
person, whether known or unknown, has been guilty of a designated offence,
with an offer to prove the fact, and a request that the offender may be
punished.
     2. To have a legal effect, the complaint must be supported by such
evidence as shows that an offence has been committed, and renders it certain
or probable that it was committed by the person named or described in the
complaint.