to curse and swear with great facility. (The trooper here refers to a soldier.) Mrs. Wilson was known to swear like a trooper on occasion. The clerk started swearing like a trooper, and the customer started crying.
Freely utter profanity or obscenity, as in The teacher was shocked when she heard one of the fathers begin to swear like a trooper. The troopers in this term were the cavalry, who were singled out for their swearing from the early 1700s on.