The meaning of MP differs depending on where the term is used. When talking about the British government, the abbreviation stands for "member of parliament." When used in the context of the U.S. armed forces, it stands for "military police."
Members of parliament are the U.K. equivalent of members of the U.S. Congress. There are 650 members of parliament, compared to 435 members of the U.S. House of Representatives and 100 members of the U.S. Senate.
The military police are another division of the Army, Navy or Marine Corps that can go out on tactical maneuvers or serve as the law enforcement arm of the armed forces.