- a garment of coarse haircloth, worn next to the skin as a penance by ascetics and penitents.
- self-imposed punishment, suffering, sacrifice, or penance.
- a shirt made of haircloth worn next to the skin as a penance
- a secret trouble or affliction
A self-imposed punishment or penance, as in I apologized a dozen times—do you want me to wear a hair shirt forever? This term, mentioned from the 13th century on, alludes to wearing a coarse, scratchy hair shirt, the practice of religious ascetics. Its figurative use dates from the mid-1800s.