A system feature that enables one system entity to signal information to another by modulating its own use of a system resource in such a way as to affect system response time observed by the second entity. See: covert channel.
(IETF RFC 4949 Ver 2)
Covert channel in which one process signals information to another process by modulating its own use of system resources (e.g., central processing unit time) in such a way that this manipulation affects the real response time observed by the second process.
NIST SP 800-53 Rev. 4 under Covert Timing Channel