verb

• (intransitive, largely obsolete) To commit adultery.
  "ca 1644, John Milton, "The Doctrine and Discipline of Divorce", Book II, Chap. 18. Nevertheleſs, as I find that Grotius on this place hath obſerved the Chriſtian emperors, Theodoſius the IId and Juſtinian, men of high wiſdom and reputed piety, decreed it to be a divorcive fornication, if the wife attempted either againſt the knowledge, or obſtinately againſt the will of her huſband, ſuch things as gave open ſuſpicion of adulterizing, as the wilful haunting of feaſts, and invitations with men not of her near kindred, the lying forth of her houſe, without probable cauſe, the frequenting of threatres againſt her huſband's mind, her endeavour to prevent or deſtroy conception."
• (ambitransitive, uncommon) To adulterate.