Exotic matter

Exotic matter is a theoretical concept. It covers any material which violates one or more classical conditions or is not made of known baryonic particles. Such materials would possess qualities like negative mass or being repelled rather than attracted by gravity. It is used in certain speculative theories, such as on the construction of wormholes.

The term is also casually attached to any material which would be difficult to produce (such as metallic hydrogen or a Bose-Einstein condensate) or which exhibits unusual properties (such as fullerenes or nanotubes), even though these materials are relatively mundane in their composition.

Compare to strange matter, dark matter, WIMP.