Personally Identifiable Information; Any representation of information that permits the identity of an individual to whom the information applies to be reasonably inferred by either direct or indirect means.
Source(s):
NIST SP 800-79-2 from EGovAct

  Information that can be used to distinguish or trace an individual’s identity, either alone or when combined with other information that is linked or linkable to a specific individual.
Source(s):
NIST SP 1800-27B under Personally Identifiable Information from NIST SP 800-37 Rev. 2
NIST SP 800-37 Rev. 2 under personally identifiable information
NIST SP 800-53 Rev. 5 under personally identifiable information from OMB Circular A-130 (2016)
NIST SP 800-53A Rev. 5 under personally identifiable information from OMB Circular A-130 (2016)
NIST SP 800-53B under personally identifiable information from OMB Circular A-130 (2016)
NISTIR 8062 under Personally Identifiable Information from OMB Circular A-130

  Any information about an individual maintained by an agency, including (1) any information that can be used to distinguish or trace an individual’s identity, such as name, social security number, date and place of birth, mother‘s maiden name, or biometric records; and (2) any other information that is linked or linkable to an individual, such as medical, educational, financial, and employment information.
Source(s):
NISTIR 8053 under personally identifiable information from GAO Report 08-536, NIST SP 800-122