To keep back, as for future use or for a special purpose. To set or cause to be set apart for a particular person or use. See Synonyms at book. To keep or secure for oneself; retain: I reserve the right to disagree. See Synonyms at keep. Something kept back or saved for future use or a special purpose. The act of reserving. The keeping of one's feelings, thoughts, or affairs to oneself. Self-restraint in expression; reticence: "One feels it everywhere, a quality of reserve, something held back\u201d ( Rollene W. Saal). Lack of enthusiasm; skeptical caution. An amount of capital held back from investment in order to meet probable or possible demands. A reservation of public land: a forest reserve. An amount of a mineral, fossil fuel, or other resource known to exist in a particular location and to be exploitable: the discovery of large oil reserves. A fighting force kept uncommitted until strategic need arises. Often used in the plural. The part of a country's armed forces not on active duty but subject to call in an emergency. Held in or forming a reserve: a reserve supply of food. in reserve Kept back, set aside, or saved.