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Jyutping caa4 sau3
Pinyin chá xiù

Definitions (Wiktionary)
  1. noun
    yellow-brown substance on teaware (usually after long use); tea stain
Definitions (Kaifangcidian)
  1. (沒有對應漢語詞彙)

茶鏽 [-锈]

Jyutping
Pinyin chá xiù

Definitions (CC-CEDICT)
  1. tea stain (on the inside of a tea pot, tea cup etc)