48 C.F.R. § 47.501
As used in this subpart-
Dry bulk carrier means a vessel used primarily for the carriage of shipload lots of homogeneous unmarked nonliquid cargoes such as grain, coal, cement, and lumber.
Dry cargo liner means a vessel used for the carriage of heterogeneous marked cargoes in parcel lots. However, any cargo may be carried in these vessels, including part cargoes of dry bulk items or, when carried in deep tanks, bulk liquids such as petroleum and vegetable oils.
Foreign-flag vessel means any vessel of foreign registry including vessels owned by U.S. citizens but registered in a nation other than the United States.
Government vessel means a vessel owned by the U.S. Government and operated directly by the Government or for the Government by an agent or contractor, including a privately owned U.S.-flag vessel under bareboat charter to the Government.
Privately owned U.S.-flag commercial vessel means a vessel
Tanker means a vessel used primarily for the carriage of bulk liquid cargoes such as liquid petroleum products, vegetable oils, and molasses.
U.S.-flag vessel when used independently means either a Government vessel or a privately owned U.S.-flag commercial vessel.
48 C.F.R. §47.501