substitute in WordNet English dictionary

1. serving or used in place of another
   "an alternative plan"
   alternate  alternative  substitute 
   
2. artificial and inferior
   "ersatz coffee"; "substitute coffee"
   ersatz  substitute 
   
3. capable of substituting in any of several positions on a team
   "a utility infielder"
   utility  substitute 
   

1. 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"
   stand-in  substitute  relief  reliever  backup  backup man  fill-in 
   
2. a person or thing that takes or can take the place of another
   substitute  replacement 
   
3. an athlete who plays only when a starter on the team is replaced
   substitute  reserve  second-stringer 
   

1. act as a substitute
   "She stood in for the soprano who suffered from a cold"
   substitute  deputize  deputise  step in 
   
2. 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"
   substitute  replace  interchange  exchange 
   
3. 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"
   substitute  sub  stand in  fill in