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Jyutping zi6 haai1
Pinyin zì hāi

Definitions (Wiktionary)
  1. verb, neologism, slang
    to get hyper by oneself; to keep oneself entertained; to amuse oneself

自嗨 [--]

Jyutping
Pinyin zì hāi

Definitions (CC-CEDICT)
  1. (slang) to have fun by oneself
  2. to amuse oneself