WordNet records no synonym and no antonym for catacomb. 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.
an underground tunnel with recesses where bodies were buried (as in ancient Rome)
Synonyms, antonyms and the broader and narrower relations for catacomb come from Princeton University’s WordNet. Full sources and licences.