take advantage of sb . 's undefended state to attack
As a Chinese idiom, Pinyin is ch é NGX ū D ǎ ox ì, which means that the words are just to the point. It is compared to percussion. From Lao Can's travels.
The origin of Idioms
Chapter 10 of Lao Can's Travels: "Huang Long raises the chime to strike, and on the chime, he clangs, harmonizes, and takes advantage of the gap."
Idiom usage
To act as a predicate or attributive
take advantage of sb . 's undefended state to attack
hear readily without comprehending what is heard - ěr shí zhī tán
not of imposing stature but strong and capable - duǎn xiǎo jīng hàn