Incident

An occurrence that actually or potentially jeopardizes the confidentiality, integrity, or availability of an information system or the information the system processes, stores, or transmits or that constitutes a violation or imminent threat of violation of security policies, security procedures, or acceptable use policies. 

See the following for more information: 
NIST SP 800-53 Rev. 4 under Incident (FIPS 200) 
FIPS 200 under INCIDENT 
NIST SP 800-128 under Incident (FIPS 200) 
NIST SP 800-137 under Incident (FIPS 200) 
NIST SP 800-12 Rev. 1 under Incident (FIPS 200) 
NISTIR 8183 under Incident (Framework for Improving Critical Infrastructure Cybersecurity, version 1.0) 
NIST SP 800-82 Rev. 2 under Incident (FIPS 200, NIST SP 800-53) 

NIST SP 800-171 Rev. 1 (FIPS 200 – Adapted) 
CNSSI 4009-2015 under security incident (NISTIR 7298 Rev. 2) 
 
An occurrence that results in actual or potential jeopardy to the confidentiality, integrity, or availability of an information system or the information the system processes, stores, or transmits or that constitutes a violation or imminent threat of violation of security policies, security procedures, or acceptable use policies.

See CNSSI 4009-2015 (FIPS 200) for more information. 
See NIST SP 800-61 Rev. 2 under Computer Security Incident for more information. 
 
A violation or imminent threat of violation of computer security policies, acceptable use policies, or standard security practices. 

See  NIST SP 800-61 Rev. 2 under Incident for more information.