WordNet records no synonym and no antonym for centavo. 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.
a fractional monetary unit of several countries: El Salvador and Sao Tome and Principe and Brazil and Argentina and Bolivia and Colombia and Cuba and the Dominican Republic and Ecuador and El Salvador and Guatemala and Honduras and Mexico and Nicaragua and Peru and the Philippines and Portugal
Synonyms, antonyms and the broader and narrower relations for centavo come from Princeton University’s WordNet. Full sources and licences.