When used in sections 7-467 to 7-477, inclusive:

(1) “Municipal employer” means any political subdivision of the state, including any town, city, borough, district, district department of health, school board, housing authority or other authority established by law, a private nonprofit corporation which has a valid contract with any town, city, borough or district to extinguish fires and to protect its inhabitants from loss by fire, and any person or persons designated by the municipal employer to act in its interest in dealing with municipal employees;

(2) “Employee” means any employee of a municipal employer, whether or not in the classified service of the municipal employer, except elected officials, administrative officials, board and commission members, certified teachers, part-time employees who work less than twenty hours per week on a seasonal basis, department heads and persons in such other positions as may be excluded from coverage under sections 7-467 to 7-477, inclusive, in accordance with subdivision (2) of § 7-471;

(3) “Seasonal basis” means working for a period of not more than one hundred twenty calendar days in any calendar year;

(4) “Department head” means an employee who heads any department in a municipal organization, has substantial supervisory control of a permanent nature over other municipal employees, and is directly accountable to the board of selectmen of a town, city or borough not having a charter or special act form of government, or to the chief executive officer of any other town, city or borough;

(5) “Department” means any major functional division in a municipal organization, notwithstanding the provisions of any charter or special act to the contrary;

(6) “Employee organization” means any lawful association, labor organization, federation or council having as a primary purpose the improvement of wages, hours and other conditions of employment among employees of municipal employers.