substitute
noun.
a person or thing that takes or can take the place of another
Synonym: replacement
noun.
an athlete who plays only when a starter on the team is replaced
noun.
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
verb.
put in the place of another; switch seemingly equivalent items
the con artist replaced the original with a fake Rembrandt|substitute regular milk for fat-free milk|synonyms can be interchanged without a changing the context's meaning
verb.
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
Synonym: fill in, stand in, sub
verb.
act as a substitute
She stood in for the soprano who suffered from a cold
adj.
capable of substituting in any of several positions on a team
a utility infielder
Synonym: utility
adj.
serving or used in place of another
an alternative plan
adj.
artificial and inferior
ersatz coffee|substitute coffee
Synonym: ersatz