WordNet records no synonym and no antonym for buggy whip. 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 horsewhip once used by a driver of a buggy
“since buggies have been replaced by cars the buggy whip has become a symbol for anything that is hopelessly outmoded”
Synonyms, antonyms and the broader and narrower relations for buggy whip come from Princeton University’s WordNet. Full sources and licences.