From WordNet (r) 3.0 (2006):
trailer
n 1: someone who takes more time than necessary; someone who
lags behind [syn: dawdler, drone, laggard, lagger,
trailer, poke]
2: an advertisement consisting of short scenes from a motion
picture that will appear in the near future [syn: preview,
prevue, trailer]
3: a large transport conveyance designed to be pulled by a truck
or tractor
4: a wheeled vehicle that can be pulled by a car or truck and is
equipped for occupancy [syn: trailer, house trailer]