the act of substituting or putting one person or thing in the place of another; as, the substitution of an agent, attorney, or representative to act for one in his absense; the substitution of bank notes for gold and silver as a circulating medium.-the state of being substituted for another.-the office or authority of one acting for another; delegated authority.-the designation of a person in a will to take a devise or legacy, either on failure of a former devisee or legatee by incapacity or unwillingness to accept, or after him.-the doctrine that christ suffered vicariously, being substituted for the sinner, and that his sufferings were expiatory.-the act or process of substituting an atom or radical for another atom or radical; metethesis; also, the state of being so substituted. see metathesis.