Arrear

Part of speech: noun (n.)

That which is behind in payment, or which remains unpaid, though due; esp. a remainder, or balance which remains due when some part has been paid; arrearage; -- commonly used in the plural, as, arrears of rent, wages, or taxes. Locke. For much I dread due payment by the Greeks Of yesterday's arrear. Cowper. I have a large arrear of letters to write. J. D. Forbes. In arrear or In arrears, behind; backward; behindhand; in debt.

Part of speech: adverb (adv.)

To or in the rear; behind; backwards. [Obs.] Spenser.