We don't have synonyms for shabbas yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are shabbat, shabbos and shabbes.
(n) :
Alternative form of Shabbat. [The Jewish Sabbath, from sundown Friday to nightfall Saturday, commemorating God's rest on the seventh day in the book of Genesis.]
(n) :
Alternative form of Shabbat. [The Jewish Sabbath, from sundown Friday to nightfall Saturday, commemorating God's rest on the seventh day in the book of Genesis.]