As used in this title:

The term “department” means one of the executive departments enumerated in , unless the context shows that such term was intended to describe the executive, legislative, or judicial branches of the government.section 1 of Title 5

The term “agency” includes any department, independent establishment, commission, administration, authority, board or bureau of the United States or any corporation in which the United States has a proprietary interest, unless the context shows that such term was intended to be used in a more limited sense.