WordNet records no synonym and no antonym for convoy. 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.
a procession of land vehicles traveling together
a collection of merchant ships with an escort of warships
the act of escorting while in transit
escort in transit
“the trucks convoyed the cars across the battle zone”
Synonyms, antonyms and the broader and narrower relations for convoy come from Princeton University’s WordNet. Full sources and licences.