What is Supplemental Appropriation?
Supplemental Appropriation meaning in finance terminology / glossary / dictionary is:
An act appropriating funds in addition to those already enacted in an annual appropriation act. Supplemental appropriations provide additional budget authority usually in cases where the need for funds is too urgent to be postponed until enactment of the regular appropriation bill. Supplementals may sometimes include items not appropriated in the regular bills for lack of timely authorizations.
reference: United States Government Accountability Office