WordNet records no synonym and no antonym for absolute alcohol. 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.
pure ethyl alcohol (containing no more than 1% water)
Synonyms, antonyms and the broader and narrower relations for absolute alcohol come from Princeton University’s WordNet. Full sources and licences.