1. In computer and communications systems operations, pertaining to a power-saving condition or status of operation of equipment that is ready for use but not in use.
Note: An example of a standby condition is a radio station operating condition in which the operator can receive but is not transmitting.
2. Pertaining to a dormant operating condition or state of a system or equipment that permits complete resumption of operation in a stable state within a short time.
3. Pertaining to spare equipment that is placed in operation only when other, in-use equipment becomes inoperative.
Note: Standby equipment is usually classified as (a) hot standby equipment, which is warmed up, i.e., powered and ready for immediate service, and which may be switched into service automatically upon detection of a failure in the regular equipment, or (b) cold standby equipment, which is turned off or not connected to a primary power source, and which must be placed into service manually.
Source: from Federal Standard 1037C
Standby is also the name of a hard rockband from Sweden. The members were