The side of a cassette tape or record that holds the primary track. / (by extension) The track on the A-side of a tape or record. / The first track on a compact disc single.

(Canada, US) A building material which covers and protects the sides of a house or other building.

present participle of side

(rail transport) 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 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) (the latter sense is probably an American definition).

simple past tense and past participle of side

Separate from the main course of a meal. / Supplementary or in addition to one's usual job or income. / Additional, surreptitious; often with a connotation of dishonesty, illegality or adultery.

plural of siding

(geography, historical) An ancient city on a small peninsula on the Mediterranean coast of Anatolia, settled by Greeks from Cyme.

straight edge of an object

plural of B-side