WordNet records no synonym and no antonym for bath. 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 vessel containing liquid in which something is immersed (as to process it or to maintain it at a constant temperature or to lubricate it)
“she soaked the etching in an acid bath”
a soaking and washing in a bathtub
“he has a good bath every morning”
Synonyms, antonyms and the broader and narrower relations for bath come from Princeton University’s WordNet. Full sources and licences.
an ancient Hebrew liquid measure equal to about 10 gallons
a town in southwestern England on the River Avon; famous for its hot springs and Roman remains