hair shirtEnglishOxford New American Dictionaryhair shirt /ˈhe(ə)r ˌSHərt, ˈhɛ(ə)r ˌʃərt / ▸ noun a shirt of haircloth, formerly worn by penitents and ascetics. ▸ adjective (hair-shirt or hair-shirted) austere and self-sacrificing: a hair-shirted existence advocated by ecofundamentalists.