a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass
A second, relatively short length of track just to the side of a railroad track, joined to the main track by switches at one or both ends, used either for unloading freight, or to allow two trains on a same track to meet (opposite directions) or pass (same direction); a railroad siding.
To divert (a locomotive or train) on to a lesser used track in order to allow other trains to pass.