1. (a) Retirement system shall mean, as the context may require, any of the following public employee retirement systems:

   1. (1) the New York State Teachers' Retirement System;
   2. (2) the New York City Employees' Retirement System;
   3. (3) the Police Pension Fund, article 2 (New York City);
   4. (4) the Fire Department Pension Fund, article 1-B (New York City);
   5. (5) the New York City Teachers' Retirement System; and
   6. (6) the Board of Education Retirement System of the City of New York.
2. (b) Administrative head shall mean, if not otherwise defined by law, the board of trustees of a retirement system, in their individual and collective capacities.
3. (c) Governmental unit shall mean New York State, any political subdivision thereof, or public authority created by such governmental unit.

The following words and phrases, as used in this Subpart, unless a different meaning is plainly required by the context, shall have the following meanings: