round trip
noun
1- a journey to one or more places and back again, especially by a route that does not cover the same ground twice（尤指不同线路的）来回旅行。
1.1
- often as modifier chiefly N. Amer. a journey to a place and back again, along the same route〈主北美〉（同线路的）往返旅行, 双程旅行：
a round trip air fare.
双程飞机票价。