WordNet records no synonym and no antonym for hysteron proteron. 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.
reversal of normal order of two words or sentences etc. (as in `bred and born')
the logical fallacy of using as a true premise a proposition that is yet to be proved
Synonyms, antonyms and the broader and narrower relations for hysteron proteron come from Princeton University’s WordNet. Full sources and licences.