Historical Reference: The most common usage is in its literal, historical sense when discussing history, watching historical dramas (a hugely popular genre in China), or visiting historical sites like the Forbidden City.
Metaphorical - “Local Tyrant”: In business or local politics, a powerful and autocratic leader might be derisively called a 土皇帝 (tǔ huángdì), meaning “local emperor” or “dirt emperor.” This implies they rule their small domain with absolute and unquestioned authority.
Metaphorical - “Spoiled Child”: The term 小皇帝 (xiǎo huángdì), or “Little Emperor,” became famous after the implementation of the One-Child Policy. It describes a male only-child who is the center of attention for his parents and both sets of grandparents, and is consequently often spoiled and demanding.
In Idioms: The term appears in common sayings, such as 皇帝不急太监急 (huángdì bù jí, tàijiàn jí) — literally, “The emperor isn't worried, but the eunuchs are.” It describes a situation where onlookers are far more anxious about an issue than the person who is actually affected.