1. A lack, shortage, or insufficiency.
2. A shortfall in paying taxes; the amount by which the tax properly due exceeds the sum of the amount of tax shown on a taxpayer’s return. — Also termed tax deficiency; income-tax deficiency; deficiency in tax.
3. The amount still owed when the property secured by a mortgage is sold at a foreclosure sale for less than the outstanding debt; esp., the shortfall between the proceeds from a foreclosure sale and an amount consisting of the principal debt plus interest plus the foreclosure costs. See deficiency judgment under JUDGMENT. [Cases: Mortgages 375, 555–562. C.J.S. Mortgages §§ 387, 391, 416–417, 674–676, 931–946, 948–959.]