綠帽子 [绿－－]

Jyutping luk6 mou2 zi2
Pinyin lǜ mào zi

Definitions (CC-CEDICT)
  1. green hat (figuratively, a symbol of being a cuckold)
Definitions (Wiktionary)
  1. noun, idiomatic
    state of having an unfaithful wife
  2. noun, literally
    green hat