Sabbatarian

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One who observes Saturday as the Sabbath, as in Judaism.
• noun One who believes in strict observance of the Sabbath.
• adjective Relating to the Sabbath or to Sabbatarians.

from The Century Dictionary.

• Pertaining to the Sabbath or its observance.
• noun One who maintains the observance of the Sabbath (in the original sense) as obligatory on Christians.
• noun One who observes the Sabbath (whether Saturday or Sunday) according to the real or supposed Jewish rules for its observance; hence, one who observes it with more than the usual strictness. In the Puritan controversies of the sixteenth century the church party maintained that the obligation to observe one day in seven as a day of rest and devotion rested not upon the fourth commandment, but upon church usage and the beneficent results arising therefrom; the Puritans maintained that the obligation was based upon the Jewish law, and that the nature of the obligation was to be deduced from the Jewish regulations. They interdicted every sort of worldly occupation and every form of pastime and recreation, and were termed Sabbatarians by their opponents; hence the later use of the term as one of reproach.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who regards and keeps the seventh day of the week as holy, agreeably to the letter of the fourth commandment in the Decalogue.
• noun A strict observer of the Sabbath.
• adjective Of or pertaining to the Sabbath, or the tenets of Sabbatarians.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A person who regards and keeps the seventh day of the week ("Saturday", the Israelite or Jewish Sabbath) as holy in conformity with the fourth commandment of the Decalogue, such as an Orthodox Jew, Seventh-day Adventist, Seventh Day Baptist, a member of the Church of God (Seventh Day); a Sabbath-keeper, a Saturday-keeper.
• noun A person who regards and keeps the first day of the week as holy and often considers it as a replacement for the seventh-day Sabbath, a Sunday-keeper.
• noun A person who favors the strict observance of the Sabbath (either the seventh day or first day of the week).
• noun A member of a non-Jewish religious sect originating in Russia distinguished by observance of Jewish rites and festivals including Saturday as the day of rest.
• adjective Of or pertaining to the Sabbath, or the tenets of Sabbatarians.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun one who observes Saturday as the Sabbath (as in Judaism)
• adjective pertaining to the Sabbath and its observance