Gweilo is Cantonese. It translates as 'Ghost Man' and is used to describe a Caucasian foreigner.
Although most of China is familiar with this word only Cantonese speakers use it as a derogative way of describing a white person.
It is considered highly offensive in Mandarin China and with some white people.
A Cant (Cantonese person): "Did Gweilo like his dessert?"
Cant waiter: "Yes he did."
White mixed European male who ate THE dessert (and knew what the word meant) remarked: "Did that Cant just call me a Gweilo???"