Indonesian slang term for "white (caucasian) person". From the word "Belanda" (orang Belanda = Dutch person). Similar to Indonesian slang "bule" (perhaps derived from "albino" ?). Now often used to refer to any light skinned foreigner. Whether either word (londoh -or- bule) is derogatory or not depends on the context and how it's said.
Temanku Charles orang londoh. Temanku Charles orang bule. My friend Charles is a Caucasian/white person/foreigner.