From Longman Dictionary of Contemporary Englishhair shirtˌhair ˈshirt noun [countable] RRa shirt made of rough uncomfortable cloth containing hair, worn in the past by some religious people to punish themselves
Examples from the Corpus
hair shirt• Thérèse did not possess a hair shirt, or a belt spiked with rusty nails, or a scourge.• If Cleo represented a hair shirt, he would wear it, and withstand the chafing.• Among penances approved by the Church were wearing a hair shirt which was prickly and uncomfortable, walking barefoot, and fasting.• From her childhood she sacrificed and mortified herself and wore a hair shirt.• And his hair shirt of guilt brought its perverse comfort again.• So, after luxuriating in its hair shirt for a few days, the City would have sold sterling anyway.• Under any circumstance, an official retraction is a terrible hair shirt. 