To put in the place of another; put in exchange.To appoint; invest with delegated authority.Put in the place or performing the functions of another; substituted.n. A person put in the place of another; one acting for or in the room of another; theatrical, an understudy; specifically (military), one who for a consideration serves in an army or navy in the place of a conscript; also, a thing serving the purpose of another.n. In calico-printing, a solution of phosphate of soda and phosphate of lime with a little glue or other form of gelatin, used as a substitute for cow-dung.n. Synonyms Proxy, alternate.In chem., to replace (an atom or group) in the molecule of a compound by another atom or group. See substituent.