1. slang In baseball and softball, a home run (a hit that results in the batter making their way around all three bases and back to home, likened to a round-trip journey). Davidson's round-tripper in the bottom of the ninth sealed the team's first World Cup championship in over 85 years. The pitcher was replaced after allowing six round-trippers in the first two innings.

2. Any journey that involves returning to the point of origin shortly after reaching the destination, especially by traveling the same route in reverse. Why don't you spend the day in town running your errands, instead of making so many round-trippers back and forth? I'll have done about four or five round-trippers to New York by the time the year is over.