WordNet records no synonym and no antonym for ontology. It is the only member of each of its synsets, 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.
(computer science) a rigorous and exhaustive organization of some knowledge domain that is usually hierarchical and contains all the relevant entities and their relations
the metaphysical study of the nature of being and existence
Synonyms, antonyms and the broader and narrower relations for ontology come from Princeton University’s WordNet. Full sources and licences.