substitute
/ˈsʌbstəˌtuːt/ /Brit ˈsʌbstəˌtjuːt/
noun
plural -tutes
[count] a person or thing that takes the place of someone or something else
sports :a player who takes the place of another player during a game
US :substitute teacher
verb
-tutes; -tuted; -tuting
[+ obj] :to put or use (someone or something) in place of someone or something else
[no obj] :to do the job of someone else or serve the function of something else
[+ obj] :to replace (one person or thing) with another