WordNet records no synonym and no antonym for actium. 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 ancient town on a promontory in western Greece
the naval battle in which Antony and Cleopatra were defeated by Octavian's fleet under Agrippa in 31 BC
Synonyms, antonyms and the broader and narrower relations for actium come from Princeton University’s WordNet. Full sources and licences.