50 U.S.C. § 1821 (Title 50—Chapter 36: Foreign Intelligence Surveillance—Subchapter B: Physical Searches)
(5) "Physical search" means any physical intrusion within the United States into premises or property (including examination of the interior of property by technical means) that is intended to result in a seizure, reproduction, inspection, or alteration of information, material, or property, under circumstances in which a person has a reasonable expectation of privacy and a warrant would be required for law enforcement purposes, but does not include (A) "electronic surveillance", as defined in section 101(f) of this Act [50 U.S.C. § 1801(f)], or (B) the acquisition by the United States Government of foreign intelligence information from international or foreign communications, or foreign intelligence activities conducted in accordance with otherwise applicable Federal law involving a foreign electronic communications system, utilizing a means other than electronic surveillance as defined in section 101(f) of this Act [50 U.S.C. § 1801(f)].
Department of Defense Regulation 5240.1-R, Procedures Governing the Activities of DOD Intelligence Components that Affect U.S. Persons, § C7.2 (Dec. 1982)
Physical search means any intrusion upon a person or a person's property or possessions to obtain items of property or information. The term does not include examination of areas that are in plain view and visible to the unaided eye if no physical trespass is undertaken, and does not include examinations of abandoned property left in a public place. The term also does not include any intrusion authorized as necessary to accomplish lawful electronic surveillance conducted pursuant to Parts 1 and 2 of Procedure 5.