急きゅう所しょを突つく

expression, godan verb (-ku)

touch the vital point; hit a sore spot

Used both literally (in martial arts or anatomy) and figuratively (to touch on a sensitive issue or weak point).

• 彼かれの一ひと言ことが急きゅう所しょを突ついて、彼かの女じょは黙だまり込こんだ。

  His remark hit a sore spot, and she fell silent.

• 柔じゅう道どうでは相あい手ての急きゅう所しょを突つくのは反はん則そくだ。

  In judo, striking an opponent's vital point is a foul.