WordNet records no synonym and no antonym for social insurance. 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.
government provision for unemployed, injured, or aged people; financed by contributions from employers and employees as well as by government revenue
Synonyms, antonyms and the broader and narrower relations for social insurance come from Princeton University’s WordNet. Full sources and licences.