WordNet (r) 3.0 (2006):

arrears
    n 1: the state of being behind in payments; "an account in
         arrears"
    2: an unpaid overdue debt

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "arrears":
   arrear, arrearage, back debts, back payments, bouncing check,
   decline, defalcation, default, defectiveness, deferred payments,
   deficit, deficit financing, delinquency, dollar gap, due, failure,
   falling short, imperfection, inadequacy, indebtedness, inferiority,
   insufficiency, liability, overdraft, short measure, shortage,
   shortcoming, shortfall, slump, underage