Since it is not originated from chinese language, its meaning is not well defined, while it is often "misued". In English it often refers to ""speechless by shock", e.g. not knowing what to say, other than knowing what to say but incapable of speaking.
There are many, many borrowed expressions in Chinese language. While these expressions are widely used, their exact meaning have never been well defined. This is one reason why Chinese language is "backward", and is inadequate for modern science and social advancement.