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plural antiparticles
(physics) A subatomic particle corresponding to another particle with the same mass, spin and mean lifetime but with charge, parity, strangeness and other quantum numbers flipped in sign; a particle that has a reversed world line to another. quotations examples
There could be whole antiworlds and antipeople made out of antiparticles. However, if you meet your antiself, don't shake hands!
1988, Stephen Hawking, A Brief History of Time: From the Big Bang to Black Holes, page 75