WordNet records no synonym and no antonym for medicare. 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.
health care for the aged; a federally administered system of health insurance available to persons aged 65 and over
Synonyms, antonyms and the broader and narrower relations for medicare come from Princeton University’s WordNet. Full sources and licences.