/trooh"peuhr/ , n.
1. a horse-cavalry soldier.
2. a mounted police officer; a police officer on horseback.
3. See state trooper .
4. a cavalry horse.
5. Chiefly Brit. a troopship.
6. like a trooper , with great energy, enthusiasm, or display: He swears like a trooper.
[ 1630-40; TROOP + -ER 1 ]