白費唇舌 [－费－－]

Jyutping baak6 fai3 seon4 sit3
Pinyin bái fèi chún shé

Definitions (CC-CEDICT)
  1. to whistle down the wind
  2. to waste one's breath (idiom)
Definitions (Wiktionary)
  1. phrase, idiomatic
    to waste one's breath