WordNet records no synonym and no antonym for united states customary system. 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.
the system of weights and measures based on the foot and pound and second and pint that dates back to colonial America but differs in some respects from the British Imperial System; today in the United States this system exists side by side with the SI system
Synonyms, antonyms and the broader and narrower relations for united states customary system come from Princeton University’s WordNet. Full sources and licences.