Noun

1. Formality and propriety of manner
2. Something kept back or saved for future use or a special purpose
3. An athlete who plays only when a starter on the team is replaced
4. (medicine) potential capacity to respond in order to maintain vital functions
5. A district that is reserved for particular purpose
6. Armed forces that are not on active duty but can be called in an emergency
7. The trait of being uncommunicative; not volunteering anything more than necessary

Verb

1. Hold back or set aside, especially for future use or contingency
2. Give or assign a resource to a particular person or cause
3. Obtain or arrange (for oneself) in advance
4. Arrange for and reserve (something for someone else) in advance