Mass. Gen. Laws ch. 258 § 1
As used in this chapter the following words shall have the following meanings:
"Acting within the scope of his office or employment", acting in the performance of any lawfully ordered military duty, in the case of an officer or soldier of the military forces of the commonwealth.
"Executive officer of a public employer", the secretary of an executive office of the commonwealth, or in the case of an agency not within the executive office, the attorney general; the adjutant general of the military forces of the commonwealth; the county commissioners of a county; the mayor of a city, or as designated by the charter of the city; the selectmen of a town or as designated by the charter of the town; and the board, directors, or committee of a district in the case of the public employers of a district, in the case of the Massachusetts Bay Transportation Authority, its general manager and, in the case of any other public employer, the nominal chief executive officer or board.
"Public attorney", the attorney who shall defend all civil actions brought against a public employer pursuant to this chapter. In the case of the commonwealth he shall be the attorney general; in the case of any county he shall be the district attorney as designated in sections twelve and thirteen of chapter twelve; in the case of a city or town he shall be the city solicitor or town counsel, or, if the town has no such counsel, an attorney employed for the purpose by the selectmen; in the case of a district he shall be an attorney legally employed by the district for that purpose; and, in the case of the Massachusetts Bay Transportation Authority, the attorney shall be the general counsel. A public attorney may also be an attorney furnished by an insurer obligated under the terms of a policy of insurance to defend the public employer against claims brought pursuant thereto.
"Public employee", elected or appointed, officers or employees of any public employer, whether serving full or part-time, temporary or permanent, compensated or uncompensated, and officers or soldiers of the military forces of the commonwealth. For purposes of this chapter, the term "public employee" shall include an approved or licensed foster caregiver with respect to claims against such caregiver by a child in the temporary custody and care of such caregiver or an adult in the care of such caregiver for injury or death caused by the conduct of such caregiver; provided, however, that such conduct was not intentional, or wanton and willful, or grossly negligent. For this purpose, a caregiver of adults means a member of a foster family, or any other individual, who is under contract with an adult foster care provider as defined and certified by the division of medical assistance.
"Public employer", the commonwealth and any county, city, town, educational collaborative, or district, including the Massachusetts Department of Transportation, the Massachusetts Bay Transportation Authority, any duly constituted regional transit authority and the Massachusetts Turnpike Authority and any public health district or joint district or regional health district or regional health board established pursuant to the provisions of section twenty-seven A or twenty-seven B of chapter one hundred and eleven, and any department, office, commission, committee, council, board, division, bureau, institution, agency or authority thereof including a local water and sewer commission including a municipal gas or electric plant, a municipal lighting plant or cooperative which operates a telecommunications system pursuant to section 47E of chapter 164, department, board and commission, which exercises direction and control over the public employee, but not a private contractor with any such public employer, the Massachusetts Port Authority, or any other independent body politic and corporate. With respect to public employees of a school committee of a city or town, the public employer for the purposes of this chapter shall be deemed to be said respective city or town.
"Serious bodily injury", bodily injury which results in a permanent disfigurement, or loss or impairment of a bodily function, limb or organ, or death.
Mass. Gen. Laws ch. 258, § 258:1