n The part of a loom that carries the woof back and forth between the warpthreads
n A transportservice (such as a bus or train) that goes back and forth between two places.
n Any other item that moves repeatedly back and forth between two positions, possibly transporting something else with it between those points (such as, in chemistry, a molecular shuttle).
v (intransitive) To go back and forth between two places.
v (transitive) To transport by shuttle or by means of a shuttle service.