rustler
  積極分子,活躍的人,偷家畜的賊
  Rus·tler n.
  1. One who, or that which, rustles.
  2. A bovine animal that can care for itself in any circumstances; also, an alert, energetic, driving person. [Slang, Western U.S.]
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  rustler
       n : someone who steals livestock (especially cattle) [syn: cattle
           thief]