The abbreviation of the province is 桂 (Gui), which comes from Guilin, a major city in the autonomous region.
Full name Guangxi Zhuang Autonomous Region.
Pinyin transliteration of Mandarin 廣西／广西 (Guǎngxī). 廣／广 (guǎng) itself means "expanse", and has been associated with the region since the creation of Guang Prefecture in 226 AD. "Guangxi" and neighbouring Guangdong literally mean "Guang West" and "Guang East". Together, Guangdong and Guangxi are called the "Two Guangs" (兩廣／两广 (Liǎngguǎng) Liǎngguǎng).