A fully operational offsite data processing facility equipped with hardware and software, to be used in the event of an information system disruption.
Source: NIST CNSSI 4009-2015 from NIST SP 800-34 Rev. 1
NIST SP 800-34 Rev. 1 under Hot Site
An alternate facility that already has in place the computer, telecommunications, and environmental infrastructure required to recover critical business functions or information systems.