WordNet records no synonym and no antonym for acid value. 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.
(chemistry) the amount of free acid present in fat as measured by the milligrams of potassium hydroxide needed to neutralize it
“as the glycerides in fat slowly decompose the acid value increases”
Synonyms, antonyms and the broader and narrower relations for acid value come from Princeton University’s WordNet. Full sources and licences.