WordNet records no synonym and no antonym for block grant. 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 grant of federal money to state and local governments to support social welfare programs
“block grants reduce federal responsibility for social welfare”
Synonyms, antonyms and the broader and narrower relations for block grant come from Princeton University’s WordNet. Full sources and licences.