The Collaborative International Dictionary of English v.0.48:

Thievish \Thiev"ish\, a.
   1. Given to stealing; addicted to theft; as, a thievish boy,
      a thievish magpie.
      [1913 Webster]

   2. Like a thief; acting by stealth; sly; secret.
      [1913 Webster]

            Time's thievish progress to eternity. --Shak.
      [1913 Webster]

   3. Partaking of the nature of theft; accomplished by
      stealing; dishonest; as, a thievish practice.
      [1913 Webster]

            Or with a base and biosterous sword enforce
            A thievish living on the common road. --Shak.
      [1913 Webster] -- Thiev"ish*ly, adv. --
      Thiev"ish*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

thievishness
    n 1: having a disposition to steal [syn: thievishness,
         larcenous]