What does "substitute" mean?

Substitute: One who, or that which, is substituted or put in the place of another; one who acts for another; that which stands in lieu of something else; specifically (Mil.), a person who enlists for military service in the place of a conscript or drafted man. Hast thou not made me here thy substitute Milton. Ladies [in Shakespeare's age] . . . wore masks as the sole substitute known to our ancestors for the modern parasol. De Quincey.

Additional senses

  1. 2.To put in the place of another person or thing; to exchange. Some few verses are inserted or substituted in the room of others. Congreve.

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