capable of substituting in any of several positions on a team, serving or used in place of another, artificial and inferior, noun_ a person or thing that takes or can take the place of another, an athlete who plays only when a starter on the team is replaced, 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, verb_ act as a substitute, be a substitute, put in the place of another; switch seemingly equivalent items, transitive verb_ To put in the place of another person or thing; to exchange, To use in place of something else, with the same function, sports To remove (a player) from the field of play and bring on another in his place, intransitive verb_ To take the place of another, To put or use (a person or thing) in place of another, Chemistry To replace (one or more atoms or groups in a compound) by other atoms or groups