What is Body Politic?

Legal Definition
The body politic is a metaphor that regards a nation as a corporate entity, likened to a human body. Here the word "politic" is a postpositive adjective: this is "a body of a politic nature", rather than "a politic of a bodily nature". A body politic comprises all the people in a particular country, considered as a single group. The analogy typically includes reference to the top of the government as head of state, though the analogy may also be extended to other anatomical parts, as in political readings of Aesop's fable of "The Belly and the Members".

A later European reference to the concept appears in The Book of the Body Politic (1407) by poet and court writer Christine de Pizan, in which she admits having borrowed the concept from a letter of Plutarch's to the Roman Emperor Trajan but does not mention John of Salisbury's work, Policraticus. The metaphor appears in the French language as the corps-├ętat. The metaphor was elaborated in the Renaissance, and subsequently, as medical knowledge based on Galen was challenged by thinkers such as William Harvey. Analogies were drawn between supposed causes of disease and disorder and their equivalents in the political field, viewed as plagues or infections that might be remedied with purges and nostrums.
-- Wikipedia
Legal Definition
Government, corporations. When applied to the government this phrase signifies the state.

2. As to the persons who compose the body politic, they take collectively the name, of people, or nation; and individually they are citizens, when considered in relation to their political rights, and subjects as being submitted to the laws of the state.

3. When it refers to corporations, the term body politic means that the members of such corporations shall be considered as an artificial person.
-- Bouviers Law Dictionary
Legal Definition
A term applied to a corporation, which is usually designated as a "body corporate and politic." The term is particularly appropriate to a public corporation invested with powers and duties of government. It is often used, in a rather loose way, to designate the state or nation or sovereign power, or the government of a county or municipality, without distinctly connoting any express and individual corporate character. Munn v. Illinois, 94 U. S. 124, 24 L. Ed. 77; Coyle v. Mcln-tire, 7 Houst. (Del.) 44, 30 Atl. 728, 40 Ain. St. Rep. 109; Warner v. Beers, 23 Wend. (N. Y.) 122; People v. Morris, 13 Wend. (N. Y.) 334.
-- Black's Law Dictionary
Legal Definition
A municipal corporation. See 24 Am. St. Rep. 67.
-- Ballentine's Law Dictionary