Any information related to a threat that might help an organization protect itself against a threat or detect the activities of an actor. Major types of threat information include indicators, TTPs, security alerts, threat intelligence reports, and tool configurations.
NIST SP 800-150
Analytical insights into trends, technologies, or tactics of an adversarial nature affecting information systems security.
NIST SP 800-137
(CNSSI 4009 - Adapted)