WordNet records no synonym and no antonym for docetism. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the heretical doctrine (associated with the Gnostics) that Jesus had no human body and his sufferings and death on the cross were apparent rather than real
Synonyms, antonyms and the broader and narrower relations for docetism come from Princeton University’s WordNet. Full sources and licences.