WordNet (r) 3.0 (2006):

round trip
    n 1: a trip to some place and back again

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "round trip":
   ambit, beat, campaign, circle, circuit, course, cycle, excursion,
   expedition, full circle, grand tour, jaunt, journey, junket, lap,
   loop, orbit, outing, package tour, peregrination, pilgrimage,
   pleasure trip, progress, revolution, round, roundabout, rounds,
   rubberneck tour, run, safari, sally, shoot, stalk, tour, trek,
   trip, turn, voyage, walk