political subdivision
(4) Definitions For purposes of this subsection— (A) The term “general retirement system” means any pension, annuity, retirement, or similar fund or system established by a State or by a political subdivision thereof for employees of the State, political subdivision, or both; but such term shall not include such a fund or system which covers only service performed in positions connected with the operation of its public transportation system. (B) A transportation system or a part thereof shall be considered to have been acquired by a State or political subdivision from private ownership if prior to the acquisition service performed by employees in connection with the operation of the system or part thereof acquired constituted employment under this chapter or subchapter A of chapter 9 of the Internal Revenue Code of 1939 or was covered by an agreement made pursuant to section 218 of the Social Security Act and some of such employees became employees of the State or political subdivision in connection with and at the time of such acquisition. (C) The term “political subdivision” includes an instrumentality of— (i) a State, (ii) one or more political subdivisions of a State, or (iii) a State and one or more of its political subdivisions.