Definition of side wing in US English:

side wing

noun

  • 1Architecture a wing projecting from the side of a building.

  • 2Theatre a piece of scenery or movable screen at the side of a stage; (in plural) the areas to either side of a stage out of view of the audience; the wings.

Origin

Late 17th century; earliest use found in John Fryer (d. 1733), traveller and writer.