Source : Webster's Revised Unabridged Dictionary (1913)

Weasel \Wea"sel\, n. [OE. wesele, AS. wesle; akin to D. wezel,
   G. wiesel, OHG. wisala, Icel. hreyiv[=i]sla, Dan. v["a]sel,
   Sw. vessla; of uncertain origin; cf. Gr. ?, ?, cat, weasel.]
   (Zo["o]l.)
   Any one of various species of small carnivores belonging to
   the genus {Putorius}, as the ermine and ferret. They have a
   slender, elongated body, and are noted for the quickness of
   their movements and for their bloodthirsty habit in
   destroying poultry, rats, etc. The ermine and some other
   species are brown in summer, and turn white in winter; others
   are brown at all seasons.

   {Malacca weasel}, the rasse.

   {Weasel coot}, a female or young male of the smew; -- so
      called from the resemblance of the head to that of a
      weasel. Called also {weasel duck}.

   {Weasel lemur}, a short-tailed lemur ({Lepilemur
      mustelinus}). It is reddish brown above, grayish brown
      below, with the throat white.

Source : WordNet®

weasel
     n : small carnivorous mammal with short legs and elongated body
         and neck

Source : Free On-Line Dictionary of Computing

weasel
     
         (Cambridge) A naive user, one who deliberately
        or accidentally does things that are stupid or ill-advised.
        Roughly synonymous with {loser}.
     
        [{Jargon File}]
     
        (1995-03-21)