barbershop talk; idle chatter
Refers to casual, often opinionated conversation that takes place in a barbershop, or by extension any similar informal, know-it-all discussion.
The barbershop talk is in full swing.
His talk is always like barbershop chatter.
Compound of 床屋 (barber) and 談義 (discussion, talk). The exact historical derivation is uncertain, but it refers to the kind of informal, opinionated conversation stereotypically heard in barbershops.