Section 126. The following words, as used in sections one hundred and twenty-six to one hundred and thirty-two, inclusive, shall have the following meanings, unless a different meaning is plainly required by the context:
''Application statement'', a writing signed by an incumbent in an appointive office which shall include a request for tenure in said office, the name, residential address and title of the office of such incumbent, and the number of years such incumbent has held such office continuously. The writing may also be signed by a department head requesting tenure for members of his department who have held offices for five or more consecutive years.
''Appointive office'', any public office other than an office which is required to be filled by popular vote periodically in a city, town or district, but not including an office within the classified civil service, an office on a board, commission or committee which has two or more members, a teacher or officer in a school department or system, any office which is filled by appointment made by the governor, or any office in an authority, board, commission or other public body which is a separate corporation from the city, town or district in which it exercises powers.
''District'', a fire, water, sewer, light, improvement or other district with such powers which is wholly contained within a city or town.
''Tenure'', the holding of an appointive office under the provisions of sections one hundred and twenty-seven to one hundred and thirty-two, inclusive, in a city, town or district without the necessity of periodic reappointment.
The titles of particular municipal officers as used in these said sections shall be construed to mean officers, however titled, who exercise powers similar to those exercised by officers holding titles so used.