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).
He's loose-lipped, so you'd better not tell him secrets.
Frivolous talk over drinks can sometimes cause problems later.
humorous story with a punch line
Compound of 軽 (light, frivolous) and 口 (mouth, speech). The exact historical derivation is uncertain, but the meaning is transparent from its components.