siding

(noun) a short stretch of railroad track used to store rolling stock or enable trains on the same line to pass. Synonyms: railroad siding, turnout, sidetrack.

(noun) material applied to the outside of a building to make it weatherproof.

(verb) take sides for or against. Synonyms: side. Examples: "Who are you widing with?." "I"m siding against the current candidate."