infusion has 1 distinct synonym spread across 1 of its 4 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 solution obtained by steeping or soaking a substance (usually in water)
the process of extracting certain active properties (as a drug from a plant) by steeping or soaking (usually in water)
(medicine) the passive introduction of a substance (a fluid or drug or electrolyte) into a vein or between tissues (as by gravitational force)
the act of infusing or introducing a certain modifying element or quality
“the team's continued success is attributable to a steady infusion of new talent”
Synonyms, antonyms and the broader and narrower relations for infusion come from Princeton University’s WordNet. Full sources and licences.