D defs.my
Entry 4 senses Webster, 1913

Trooper

· Troop·er · IPA /ˈtɹuːpə(ɹ)/
01 n. A soldier in a body of cavalry; a cavalryman; also, the horse of a cavalryman.
  1. 1.
    A soldier in a body of cavalry; a cavalryman; also, the horse of a cavalryman.
  2. 2.
    A state police officer; -- also called state trooper.[U. S.] Also: state trooper
  3. 3.
    A mounted policeman.[Australia]
  4. 4.
    Trouper.
Phrases & compounds
like a trooper — with energy, endurance, or enthusiasm; as, to work like a trooper.