WordNet records no synonym and no antonym for marxism. 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.
the economic and political theories of Karl Marx and Friedrich Engels that hold that human actions and institutions are economically determined and that class struggle is needed to create historical change and that capitalism will ultimately be superseded by communism
Synonyms, antonyms and the broader and narrower relations for marxism come from Princeton University’s WordNet. Full sources and licences.