acquirer 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 person who acquires something (usually permanently)
a corporation gaining financial control over another corporation or financial institution through a payment in cash or an exchange of stock
the financial institution that dispenses cash in automated teller machines and collects a fee from the bank that issued the credit card
a credit card processing bank; merchants receive credit for credit card receipts less a processing fee
Synonyms, antonyms and the broader and narrower relations for acquirer come from Princeton University’s WordNet. Full sources and licences.