mandate has 3 distinct synonyms spread across 2 of its 6 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
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 document giving an official instruction or command
a territory surrendered by Turkey or Germany after World War I and put under the tutelage of some other European power until they are able to stand by themselves
Synonyms, antonyms and the broader and narrower relations for mandate come from Princeton University’s WordNet. Full sources and licences.
the commission that is given to a government and its policies through an electoral victory