We don't have synonyms for antiparticles yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are antiparticle, anti-particle and antipartticle.
(n) :
(particle 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.
(n) :
(particle 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.