(slang, Britain, New Zealand, Australia) A secondary lover, a mistress.

(baseball) To get the third out of an inning.

(music) A record, released as a single, with an album track on each side, rather than having a B-side.

Having two sides, bilateral. / Reversible. / (algebra) Whose salient properties apply when (the specified object) appears on either side of a given binary operator.

Alternative spelling of sidelobe

The uppermost side of anything

(video games) A video game where the player views the world from the side, controlling a character who mostly travels horizontally (usually left to right) through a level.

plural of side scroller

Alternative form of sideshow

Having many sides; polygonal / Having many aspects