A disbursement is a payment made by a Federal agency in order to fulfill the requirement of a legal obligation of budget authority. Agencies disburse against obligated balances and adjust obligated balances to reflect actual obligations during the period of availability.
GAO Glossary of Terms and Definition (September 2005)
Amounts paid by federal agencies, by cash or cash equivalent, during the fiscal year to liquidate government obligations. “Disbursement” is used interchangeably with the term “outlay.” In budgetary usage, gross disbursements represent the amount of checks issued and cash or other payments made, less refunds received. Net disbursements represent gross disbursements less income collected and credited to the appropriation or fund account, such as amounts received for goods and services provided. (See also Outlay; Expenditure.)
Treasury Financial Manual
Treasury Financial Manual: Overall Disbursing Rules for All Federal Agencies (Department of the Treasury) 2000 [PDF]