軽かる口くち

noun, noun which may take the genitive case particle 'no'

talkative; loose-lipped; frivolous talk

Describes a person who talks too much or carelessly, often revealing things better left unsaid. Can also refer to light, joking, or frivolous conversation. Common in phrases like 軽口を叩く (to chatter thoughtlessly).

• 彼かれは軽かる口くちだから、秘ひ密みつを話はなすのはやめたほうがいい。

  He's loose-lipped, so you'd better not tell him secrets.

• 酒さけの席せきでの軽かる口くちが、後あとで問もん題だいになることもある。

  Frivolous talk over drinks can sometimes cause problems later.