verb/paʁ.le ɑ̃ l‿ɛʁ/
to waste one's breath (to speak without being listened to); to blow smoke; to talk through one's hat (to speak about issues one doesn't understand)
Synonyms: parler dans le vide, parler dans le vent, parler à un mur, parler à tort et à travers, parler pour ne rien dire