substitute

(s) capable of substituting in any of several positions on a team
- a utility infielder
utility,
(s) serving or used in place of another
- an alternative plan
alternative, alternate,
(s) artificial and inferior
- ersatz coffee
- substitute coffee
ersatz,

(n) a person or thing that takes or can take the place of another replacement,
(n) an athlete who plays only when a starter on the team is replaced second-stringer, reserve,
(n) someone who takes the place of another (as when things get dangerous or difficult)
- the star had a stand-in for dangerous scenes
- we need extra employees for summer fill-ins
backup man, fill-in, reliever, stand-in, backup, relief,

(v) put in the place of another; switch seemingly equivalent items
- the con artist replaced the original with a fake Rembrandt
- substitute regular milk with fat-free milk
- synonyms can be interchanged without a changing the context's meaning
interchange, replace, exchange,
(v) be a substitute
- The young teacher had to substitute for the sick colleague
- The skim milk substitutes for cream--we are on a strict diet
stand in, sub, fill in,
(v) act as a substitute
- She stood in for the soprano who suffered from a cold
deputise, deputize, step in,

utility replacement interchange replace exchange alternative alternate stand in sub fill in second-stringer reserve ersatz deputise deputize step in backup man reliever backup relief