from
The Collaborative International Dictionary of English v.0.48
Trooper \Troop"er\, n.
1. A soldier in a body of cavalry; a cavalryman; also, the
horse of a cavalryman.
[1913 Webster]
2. A state police officer; -- also called {state trooper}.
[U. S.]
[PJC]
3. A mounted policeman. [Australia]
Note: The {black troopers} of Queensland are a regiment of
aboriginal police, employed chiefly for dispersing wild
aborigines who encroach on sheep runs.
[Webster 1913 Suppl.]
4. Trouper.
[PJC]
{like a trooper}, with energy, endurance, or enthusiasm; as,
to work like a trooper.