Was talking abt something when I heard Irene (Indonesian) saying "Wah Lau". Hmmm ... guess she has been localised long enuff. Don't think the phrase is widely used in Indonesia :P
Definition:
An exclamation most frequently used to express a certain depth of emotion especially when in disbelief or disagreement. Almost equivalent to the English expression of "Oh My God!" It is originated from the Hokkien dialect and widely used in my motherland. There's no age limit in using this expression. But it certainly adds a certain degree of "beng-ness" or "lian-ness" to ur image depending on how u say it of course.
Disclaimer:
This crappy definition is just a result of me trying to stay awake in office before knocking off ... Zzzz ...