"the star had a stand-in for dangerous scenes" "we need extra employees for summer fill-ins"
"a utility infielder"
"an alternative plan"
"ersatz coffee" "substitute coffee"
"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"
"The young teacher had to substitute for the sick colleague" "The skim milk substitutes for cream--we are on a strict diet"
"She stood in for the soprano who suffered from a cold"