WordNet records no synonym and no antonym for indene. 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.
a colorless liquid hydrocarbon extracted from petroleum or coal tar and used in making synthetic resins
Synonyms, antonyms and the broader and narrower relations for indene come from Princeton University’s WordNet. Full sources and licences.