2 CFR §1108.265

1. (a)When used in conjunction with a DoD Component's award, a legally binding agreement that will result in outlays, either immediately or in the future. Examples of actions through which a DoD Component incurs an obligation include the grants or agreements officer's signature of a grant, cooperative agreement, or technology investment agreement (or modification of such an award) authorizing the recipient to use funds under the award.
2. (b)When used in conjunction with a recipient's or subrecipient's use of funds under an award or subaward, an order placed for property and services, a contract or subaward made, or a similar transaction, during a given period that requires payment during the same or a future period.