10 letters · 12 points in Scrabble
noun matter consisting of elementary particles that are the antiparticles of those making up normal substances
originFrom 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.
Etymology from Wiktionary, CC BY-SA 3.0