Source : Webster's Revised Unabridged Dictionary (1913)

Thug \Thug\, n.
   An assassin; a ruffian; a rough. ``Thugs and midnight
   rounders.'' --The Century.

Thug \Thug\, n. [Hind. thag a deceiver, robber.]
   One of an association of robbers and murderers in India who
   practiced murder by stealthy approaches, and from religious
   motives. They have been nearly exterminated by the British
   government.

Source : WordNet®

thug
     n : an aggressive and violent young criminal [syn: {hood}, {hoodlum},
          {goon}, {punk}, {tough}, {toughie}, {strong-armer}]