Definition of "siding"

noun:
- A building material which covers and protects the sides of a house or other building (called cladding in the UK).
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
- 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).
  
  from Wiktionary, Creative Commons Attribution/Share-Alike License
verb:
- Present participle of side.
  
  side
  from Wiktionary, Creative Commons Attribution/Share-Alike License