Nonce

Nonce definition in Computer Security terms:

Acronym(s): None

Definition(s): A random or non-repeating value that is included in data exchanged by a protocol, usually for the purpose of guaranteeing the transmittal of live data rather than replayed data, thus detecting and protecting against replay attacks.
Source(s): CNSSI 4009-2015 (IETF RFC 4949 Ver 2)

A time-varying value that has at most a negligible chance of repeating, for example, a random value that is generated anew for each use, a timestamp, a sequence number, or some combination of these.
Source(s): NIST SP 800-102
NIST SP 800-120

A time-varying value that has at most a negligible chance of repeating