Deficit
From ACT Wiki
1. Pensions accounting.
The excess of liabilities over assets in a funded Defined benefit pension scheme; also known as under-funding.
Example
Pension liabilities = 100
Pension assets = 90,
The deficit would be 100 - 90 = 10.
(Not to be confused with the percentage funding level which in this example would be 90 / 100 = 90%.)
2. More generally, any financial shortfall.