Abstract: Most lexicographical books define the meaning of “thrice not knowing” as “suddenly unexpectedly”. Such has flaws in incompleteness in meanings and low-calibre summary. As a matter of fact, after the Yuan dynasty the meanings of the expression began to become empty and emptied into an adverbial element, often used adverbially before a verbor verb element. In accordance with different context, it can be understood as : suddenly, all of a sudden; not knowing how, unknowingly, bewilderedly; rashly, stupidly; stealthily, secretly, quietly; straight, directly, etc.

Key words: “thrice not knowing”, emptied, context