Information gathered and activities conducted to identify, deceive, exploit, disrupt, or protect against espionage, other intelligence activities, sabotage, or assassinations conducted for or on behalf of foreign powers, organizations, or persons, or their agents, or international terrorist organizations or activities.
Sources:
CNSSI 4009-2015 from E.O. 12333 (As amended by E.O.s 13284 (2003), 13355 (2004) and 13470 (2008))

  Information gathered and activities conducted to protect against espionage, other intelligence activities, sabotage, or assassinations conducted by or on behalf of foreign governments or elements thereof, foreign organizations, or foreign persons, or international terrorist activities.
Sources:
NIST SP 800-60 Vol. 1 Rev. 1 under Counterintelligence
NIST SP 800-60 Vol. 2 Rev. 1 under Counterintelligence

  The term 'counterintelligence' means information gathered and activities conducted to protect against espionage, other intelligence activities, sabotage, or assassinations conducted by or on behalf of foreign governments or elements thereof, foreign organizations, or foreign persons, or international terrorist activities.
Sources:
NIST SP 800-59 under Counterintelligence from 50 U.S.C., Sec 401a