verb

• (transitive) To corrupt, to debase (someone or something).
  "For thus, that King violated that Oath which he ought moſt religiouſly to have ſworn to; but that he might not ſeem openly and publickly to violate it, he craftily adulterated and corrupted it; and leaſt he himſelf ſhould be accounted perjur'd, he turn'd the very Oath into a Perjury. [...] And who durſt pervert and adulterate that Law which he thought the only Obſtacle that ſtood in his way, and hindred him from perverting all the reſt of the Laws?"
• (transitive) To make less valuable or spoil (something) by adding impurities or other substances.
  "to adulterate coins, drugs, food and drink, etc."
• (transitive, archaic) To commit adultery with (someone).
• (transitive, archaic) To defile (someone) by adultery.
  "Yet ſome would perſwade us, that this abſurd opinion was King Davids; becauſe in the 51st Pſalm he cries out to God, Againſt thee onely have I ſinn'd; as if David had imagin'd that to murder Uriah and adulterate his Wife, had bin no ſinn againſt his Neighbour, when as that Law of Moſes was to the King expreſly, Deut. 17. not to think ſo highly of himſelf above his Brethren."