WordNet records no synonym and no antonym for judge advocate. 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.
an officer assigned to the judge advocate general
a staff officer serving as legal adviser to a military commander
Synonyms, antonyms and the broader and narrower relations for judge advocate come from Princeton University’s WordNet. Full sources and licences.