antimatter

• anti-matter

From anti- +‎ matter. Coined by British physicist Arthur Schuster in 1898 to describe matter that resists gravity in a jocular article in Nature titled "Potential Matter.—A Holiday Dream", but not used in a modern sense until the 1940s.

• (General American) IPA^(key): /ˈæn.tiˌmæt.ɚ/, /ˈænˌtaɪˌmæt.ɚ/, [ˈæn.tiˌmæ.ɾɚ], [ˈæ.ɾ̃iˌmæ.ɾɚ], [ˈæ.niˌmæ.ɾɚ]

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antimatter (usually uncountable, plural antimatters)

1. (physics) Matter that is composed of the antiparticles of those that constitute normal matter.
2. (physics) A form of matter that has a key property, such as charge, opposite to that of ordinary matter.

• antimatter rocket