Partial or biased in favour of one faction or demographic group. / With one competitor dominant over the other. / Out of proportion or lopsided. / Having only one side, like a Möbius strip.

(economics) Regarding the supply side of the economy.

(economics) In a market trade, the side where the supply comes from.

A note or notation made in a side margin. / A minor related mention, made as an aside, or afterthought.

(cricket) The side of the pitch away from the batsman's legs as he takes his stance at the wicket; the right side for a right-handed batsman. / (horsemanship) The right-hand side of a horse.

(slang, baseball, dated, 19th c.) three outs.

(sports) A play in American football whereby the team performing the kick-off kicks the ball the minimum distance (ten yards in most levels of play) in an attempt to immediately regain possession of the ball.

(idiomatic) To ally oneself with a given opinion, agenda or group; to support one side or viewpoint in a competition or confrontation.

To alter as a side effect.

The reverse side of a cassette tape or a phonograph record, especially a vinyl single, often containing songs not considered for airplay.