noun someone who takes the place of another (as when things get dangerous or difficult).
— synonyms: stand-in, substitute, relief, backup, backup_man, fill-in
noun a person who reduces the intensity (e.g., of fears) and calms and pacifies.
— synonyms: allayer, comforter
noun a pitcher who does not start the game.
— synonyms: relief_pitcher, fireman
Examples
“The first reliever got the last two outs of the sixth.”
“I'll be the reliever today so that you can each take a break.”