1. money that is owed and should have been paid earlier:"he was suing the lessee for the arrears of rent"Similarmoney owingoutstanding payment(s)debt(s)liabilitiesindebtednessduesbalancedeficit
Word OriginMiddle English (first used in the phrase in arrear): from arrear (adverb) ‘behind, overdue’, from Old French arere, from medieval Latin adretro, from ad- ‘towards’ + retro ‘backwards’.