A situation where two things are changed at once / (baseball) A replacement of two players simultaneously, typically so that a fielder can hit in the pitcher's spot in the batting order.

(baseball, softball) A defensive play in which two outs are recorded. / (US, colloquial) Achieving two results from one action.

(transitive) To double the quantity, amount or duration of something / (poker, by extension, intransitive) To double one's amount of chips by winning an all-in pot.

Doublespeak. / Lies, especially in a formal political statement. / (comedy) Speech which combines English (or some other language) and native-sounding gibberish for humorous effect.

(basketball) The achievement of a two-digit number of any three of points scored, assists, rebounds, blocks, or steals in a single game.

(basketball) The achievement of a two-digit number of all five of points scored, assists, rebounds, blocks, and steals in a single game.

(basketball) The achievement of a two-digit number of any four of points scored, assists, rebounds, blocks, or steals in a single game.

(astronomy) Two stars which form a stellar system, such that they orbit the point of equilibrium of their gravitational fields; a binary star.

A series of two events that causes adverse effects; a twofold blow or setback. / (by extension) A series of two events that causes positive effects; a twofold boon.

Pneumonia affecting both lungs.