To swear falsely; be false to oaths or vows; bear false witness.To render guilty of the crime of testifying falsely under oath or solemn affirmation, especially in judicial or official proceedings, or of being false to one's oaths or vows; forswear: commonly used reflexively: as, the witness perjured himself.To swear falsely to; deceive by false oaths or protestations.Synonyms Perjure, Forswear. Perjure is now technical and particular; strictly, it is limited to taking a legal oath falsely; occasionally it is used for forswear. Forswear is general, but somewhat old-fashioned.n. A perjured person.