Open English Wordnet
Nouns
(n)substitute, reserve, second-stringeran athlete who plays only when a starter on the team is replaced
(n)stand-in, substitute, relief, reliever, backup, backup man, fill-insomeone 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”
Verbs
(v)substitute, replace, interchange, exchangeput 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 changing the context's meaning”
(v)substitute, sub, stand in, fill inbe a substitute“The young teacher had to substitute for the sick colleague”, “The skim milk substitutes for cream--we are on a strict diet”
(v)substitute, deputize, deputise, step inact as a substitute“She stood in for the soprano who suffered from a cold”
Adjectives
(s)utility, substitutecapable of substituting in any of several positions on a team“a utility infielder”