antiparticle

noun1

1. •
   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.

   • There could be whole antiworlds and antipeople made out of antiparticles. However, if you meet your antiself, don't shake hands! — 1988