WordNet records no synonym and no antonym for new amsterdam. 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 settlement established by the Dutch near the mouth of Hudson River and the southern end of Manhattan Island; annexed by the English in 1664 and renamed New York
Synonyms, antonyms and the broader and narrower relations for new amsterdam come from Princeton University’s WordNet. Full sources and licences.