The Collaborative International Dictionary of English v.0.48:

Sabbatic \Sab*bat"ic\, Sabbatical \Sab*bat"ic*al\, a. [Gr. ?:
   cf. F. sabbatique.]
   Of or pertaining to the Sabbath; resembling the Sabbath;
   enjoying or bringing an intermission of labor.
   [1913 Webster]

   Sabbatical year (Jewish Antiq.), every seventh year, in
      which the Israelites were commanded to suffer their fields
      and vineyards to rest, or lie without tillage.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sabbatical
    adj 1: of or relating to the Sabbath; "Friday is a sabbatical
           day for Muslims" [syn: sabbatical, sabbatic]
    2: of or relating to sabbatical leave; "sabbatical research
       project"
    n 1: a leave usually taken every seventh year [syn:
         sabbatical, sabbatical leave]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "sabbatical":
   comfortable, festal, furlough, holiday, leave, leave of absence,
   liberty, paid holiday, paid vacation, quiet, restful,
   sabbatical leave, sabbatical year, shore leave, time off, vacation,
   vacational, weekend