de·fi·cien·cy / diˈfishənsē/ • n. (pl. -cies) a lack or shortage. ∎  a failing or shortcoming.

DEFICIENCY

A shortage or insufficiency. The amount by which federalincome taxdue exceeds the amount reported by the taxpayer on his or her return; also, the amount owed by a taxpayer who has not filed a return. The outstanding balance of a debt secured by a mortgage after the mortgaged property has been sold to satisfy the obligation at a price less than the debt.