Section 129. The following words, as used in sections one hundred and thirty to one hundred and thirty-two, inclusive, unless the context otherwise requires, or a different meaning is specifically prescribed, shall have the following meanings:—

''Commissioner'', the commissioner of insurance.

''Fund balance'', a minimum of two hundred and fifty thousand dollars or a lesser or greater amount approved by the commissioner.

''Municipal light board'', a municipal light board or commission, municipal gas and electric commission or similar body in a city or town having a municipal light board, gas and electric commission or similar body; the mayor or city manager as the case may be, of a city having no municipal light board, municipal gas and electric commission or similar body; or the selectmen of a town having no municipal light board, municipal gas and electric commission or similar body.

''Municipal electric department'', an electric department or lighting plant of a city or town, which department or plant is subject to the provisions of this chapter, or a municipally or consumer-owned electric utility outside the commonwealth. Except as otherwise specifically provided, a Massachusetts municipal electric department may exercise any of its powers or authority granted in sections one hundred and twenty-nine to one hundred and thirty-two, inclusive, through its municipal light board.

''Municipal Electric Department Self-insurance Trust Fund'' or ''Fund'', a trust fund established in accordance with the provisions of section one hundred and twenty-nine to one hundred and thirty-two, inclusive, to provide insurance to a group of two or more participating municipal electric departments.

''Insurance'', formal self-insurance or commercial insurance or a combination thereof, covering risks including, without limiting the generality of the foregoing, general liability, directors and officers, and fire insurance. Insurance shall include all layers of coverage, on either a claims made or occurrence basis and reinsurance.

''Participant'', a municipal electric department that is a member of a fund, in accordance with section one hundred and thirty, and has accepted the benefits and detriments of sections one hundred and twenty-nine to one hundred and thirty-two, inclusive;

''Trustee'', the trustee of a fund.