From Longman Dictionary of Contemporary Englishtroopertroop‧er /ˈtruːpə $ -ər/ noun 1 [countable]PMA a soldier of the lowest rank in the part of the army that uses tanks or horses2 [countable]SCP a member of a state police force in the US3 → swear like a trooper
Examples from the Corpus
trooper• And where was he going 90 minutes after the bombing when stopped by an Oklahoma trooper on Interstate 35 near Perry?• In 1994, a Maryland State trooper saw a car speeding down Interstate 95.• For decades these latter had been infiltrating the administration and even the troopers.• We dropped off the troopers and picked up wounded. 