WordNet records no synonym and no antonym for visa. 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.
approve officially
“The list of speakers must be visaed”
an endorsement made in a passport that allows the bearer to enter the country issuing it
Synonyms, antonyms and the broader and narrower relations for visa come from Princeton University’s WordNet. Full sources and licences.