1.NounA building material which covers and protects the sides of a house or other building.
"Ugh. If there's one thing I can't stand it's cheesy vinyl siding."
2.Verbpresent participle and gerund of side
"Whenever he hears an argument, he can't help siding with one party or the other."
3.NounA 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 loading or unloading freight, storing trains or other rail vehicles; or to allow two trains on a same track to meet (opposite directions) or pass (same direction) .