In this subchapter:
(4) Federal agency.—The term “Federal agency” means—
an executive department or independent establishment in the executive branch of the Government; or
(5) Field office.—
(6) Postal property.—
The term “postal property” means any property owned or leased by the United States Postal Service.
(7) Public-private partnership.—
(8) Underutilized property.—The term “underutilized property” means a portion or the entirety of any real property, including any improvements, that is used—