n. 活跃分子, 偷家畜贼

[ noun ]
someone who steals livestock (especially cattle)
<noun.person>

Rustler \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.]