A moment of total bewilderment, which usually occurs when a person has been sitting for a long time and stands up quickly, he becomes faint, yet does not lose total consciousness. This person will often fall over, but not lose total consciousness, and experience this feeling of fung-tutsu. This can also be often experienced under the influence of nitrous oxide at the dentist office. See also ding-ding-ding.
I got up really fast, and felt fung-tutsu, until total consciousness returned.