Source : Webster's Revised Unabridged Dictionary (1913)

Sabbatarian \Sab`ba*ta"ri*an\, n. [L. Sabbatarius: cf. F.
   sabbataire. See {Sabbath}.]
   1. One who regards and keeps the seventh day of the week as
      holy, agreeably to the letter of the fourth commandment in
      the Decalogue.

   Note: There were Christians in the early church who held this
         opinion, and certain Christians, esp. the {Seventh-day
         Baptists}, hold it now.

   2. A strict observer of the Sabbath.

Sabbatarian \Sab`ba*ta"ri*an\, a.
   Of or pertaining to the Sabbath, or the tenets of
   Sabbatarians.

Source : WordNet®

Sabbatarian
     adj : pertaining to the Sabbath and its observance
     n : one who observes Saturday as the Sabbath (as in Judaism)