To express annoyance, impatience, or mild reproof. An exclamation of mild reprimand, disapproval, or surprise. 'tut-tut,' as in disapproval.

honestly, I don't have any idea at all except that we sometimes use this word to express censorship - rather than uttering those obscene or curse words. :)

oh yes... Thanks Peachey

I think the right answer is the deep_blue one. But I just want to comment peachey, the "tut-tut" for Indonesian people is sound of train, may be for foreigner is different, like you said "toot-toot".

Err... that taxi-bike is called a ตุ๊กตุ๊ก = tuk-tuk ;)