Source : Webster's Revised Unabridged Dictionary (1913)

Slavish \Slav"ish\, a.
   Of or pertaining to slaves; such as becomes or befits a
   slave; servile; excessively laborious; as, a slavish life; a
   slavish dependance on the great. -- {Slav"ish*ly}, adv. --
   {Slav"ish*ness}, n.

Source : WordNet®

slavishly
     adv : in a slavish manner; "his followers slavishly believed in
           his new diet"