1. A determination made by the Office of Management and Budget which limits the amount of obligations or expenditures that may be incurred during a specified time period. An apportionment may limit all obligations to be incurred during the specified period or it may limit obligation to be incurred for a specific activity, function, project, object, or a combination thereof. The third of four phases of the DoD resource allocation process. 2. The determination and assignment of the total expected effort by percentage and/or by priority that should be devoted to the various air operations and/or geographic areas for a given period of time. 3. In the general sense, distribution for planning of limited resources among competing requirements. Specific apportionments (e.g. air sorties and forces for planning) are described as apportionment of air sorties and forces for planning, etc.