a person or thing that takes or can take the place of another
an athlete who plays only when a starter on the team is replaced
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"
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"
act as a substitute; "She stood in for the soprano who suffered from a cold"