The magnitude of harm that can be expected to result from the consequences of unauthorized disclosure of information, unauthorized modification of information, unauthorized destruction of information, or loss of information or information system availability.
Sources:
NIST SP 800-34 Rev. 1 under Impact
NIST SP 800-60 Vol. 1 Rev. 1 under Impact
NIST SP 800-60 Vol. 2 Rev. 1 under Impact

  The effect on organizational operations, organizational assets, individuals, other organizations, or the Nation (including the national security interests of the United States) of a loss of confidentiality, integrity, or availability of information or an information system.
Sources:
CNSSI 4009-2015 from FIPS 199 - Adapted
NIST SP 1800-21B under Impact
NISTIR 7621 Rev. 1 under Impact

  With respect to security, the effect on organizational operations, organizational assets, individuals, other organizations, or the Nation (including the national security interests of the United States) of a loss of confidentiality, integrity, or availability of information or a system. With respect to privacy, the adverse effects that individuals could experience when an information system processes their PII.
Sources:
NIST SP 800-172
NIST SP 800-172A
NIST SP 800-37 Rev. 2
NIST SP 800-171 Rev. 2

  The effect on organizational operations, organizational assets, individuals, other organizations, or the Nation (including the national security interests of the United States) of a loss of confidentiality, integrity, or availability of information or a system.
Sources:
NIST SP 800-161r1 from NIST SP 800-53 Rev. 5
NIST SP 800-53 Rev. 5
NIST SP 800-53A Rev. 5
NIST SP 800-53B