The Collaborative International Dictionary of English v.0.48:

Selectman \Se*lect"man\, n.; pl. Selectmen.
   One of a board of town officers chosen annually in the New
   England States to transact the general public business of the
   town, and have a kind of executive authority. The number is
   usually from three to seven in each town.
   [1913 Webster]

         The system of delegated town action was then, perhaps,
         the same which was defined in an "order made in 1635 by
         the inhabitants of Charlestown at a full meeting for
         the government of the town, by selectmen;" the name
         presently extended throughout New England to municipal
         governors.                               --Palfrey.
   [1913 Webster]

WordNet (r) 3.0 (2006):

selectman
    n 1: an elected member of a board of officials who run New
         England towns

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "selectman":
   alderman, archon, bailie, burghermaster, burgomaster,
   cabinet member, cabinet minister, chancellor, city councilman,
   city father, city manager, commissar, commissioner, councillor,
   councilman, councilwoman, county commissioner, county supervisor,
   elder, headman, induna, legislator, lord mayor, magistrate, maire,
   mayor, minister, minister of state, portreeve, reeve, secretary,
   secretary of state, supervisor, syndic, undersecretary, warden