The Collaborative International Dictionary of English v.0.48:

Delinquent \De*lin"quent\a. [L. delinquens, -entis, p. pr. of
   delinquere to fail, be wanting in one's duty, do wrong; de- +
   linquere to leave. See Loan, n.]
   Failing in duty; offending by neglect of duty.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Delinquent \De*lin"quent\, n.
   One who fails or neglects to perform his duty; an offender or
   transgressor; one who commits a fault or a crime; a culprit.
   [1913 Webster]

         A delinquent ought to be cited in the place or
         jurisdiction where the delinquency was committed.
                                                  --Ayliffe.
   [1913 Webster]

WordNet (r) 3.0 (2006):

delinquent
    adj 1: guilty of a misdeed; "delinquent minors"
    2: failing in what duty requires; "derelict (or delinquent) in
       his duty"; "neglectful of his duties"; "remiss of you not to
       pay your bills" [syn: derelict, delinquent, neglectful,
       remiss]
    3: past due; not paid at the scheduled time; "an overdue
       installment"; "a delinquent account" [syn: delinquent,
       overdue]
    n 1: a young offender [syn: delinquent, juvenile delinquent]

Moby Thesaurus II by Grady Ward, 1.0:

94 Moby Thesaurus words for "delinquent":
   aberrant, abnormal, abominable, atrocious, bad person, behindhand,
   careless, criminal, crook, culprit, deceiver, defaulter,
   defaulting, derelict, deviant, disgraceful, disregardful, evil,
   evil man, evil person, evildoer, failing, felon, gangster,
   hardly the thing, hooligan, ignominious, illegal, improper,
   in arrear, in arrears, inappropriate, incorrect, indecorous,
   infamous, late, lawbreaker, lax, levanter, malefactor, malevolent,
   malfeasant, malfeasor, miscreant, misdemeanant, misdemeanist,
   misfeasor, mobster, neglectful, negligent, nonpayer, nonpaying,
   not done, not the thing, off-base, off-color, offender,
   out-of-line, outlaw, overdue, past due, public enemy, racketeer,
   regardless, remiss, roughneck, ruffian, sacrilegious, scandalous,
   shameful, shameless, sinful, sinner, slack, tax dodger, tax evader,
   terrible, thief, transgressor, undue, unfit, unfitting, unlawful,
   unpaid, unrighteous, unseemly, unsuitable, villain, welsher,
   wicked, worker of ill, wrong, wrongdoer, wrongful



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

DELINQUENT, civil law. He who has been guilty of some crime, offence or
failure of duty.