substitute -
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"
locum,
locum tenens someone (physician or clergyman) who substitutes temporarily for another member of the same profession
stunt man,
stunt woman,
double a base hit on which the batter stops safely at second base; "he hit a double to deep centerfield"
Verb
substitute -
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"
modify,
alter,
change make less severe or harsh or extreme; "please modify this letter to make it more polite"; "he modified his views on same-gender marriage"
shift move and exchange for another; "shift the date for our class reunion"
supercede,
supersede,
supervene upon,
supplant,
replace take the place or move into the position of; "Smith replaced Miller as CEO after Miller left"; "the computer has supplanted the slide rule"; "Mary replaced Susan as the team's captain and the highest-ranked player in the school"
cover clothe, as if for protection from the elements; "cover your head!"
substitute -
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"
