WordNet records no synonym and no antonym for rip van winkle. 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.
a person oblivious to social changes
the title character in a story by Washington Irving about a man who sleeps for 20 years and doesn't recognize the world when he wakens
Synonyms, antonyms and the broader and narrower relations for rip van winkle come from Princeton University’s WordNet. Full sources and licences.