Jyutping
ngoi6 wong2 noi6 dai3
Pinyin
wài wáng nèi dì
Definitions (Wiktionary)
noun, historical
East Asian practice in which a monarch is described as a 王 (“king”) during diplomacy with the Chinese emperor, and as 皇帝 (huángdì, “emperor”) in his own country (e.g. notably in historical Vietnam)