1. In an entity, such as a system, subsystem, process, procedure, property, or equipment, that (a) provides a defined degree of assurance that the entity will continue to function during and after a natural or man-made disturbance, such as an earthquake or nuclear burst, and (b) is qualified by specifying (i) the range of conditions over which the entity will survive, (ii) the minimum acceptable level of post-disturbance functionality, and (iii) the maximum acceptable outage period. 2. In a system, such as a communications, computer, automatic data processing, information, or control system, the capability of the system to resist any interruption or disturbance of service, such as that caused by warfare, fire, earthquake, harmful radiation, or other physical or natural catastrophe rather than by electromagnetic interference or crosstalk. Synonym survivable operation. See communications survivability,  electromagnetic survivability. See also automatic data processing system,  communications system,  computer system,  condition,  continuous operation,  control system,  crosstalk,  disturbance,  electromagnetic interference,  endurability,  entity,  fiber optic equipment,  function,  functionality,  information system,  interference,  interrupt,  level,  outage,  outage period,  physical,  procedure,  process,  radiation,  range,  service,  specify,  subsystem,  system.