선종 (禪宗)에서 진리를 문답하는데 쓰는 독특한 수단. 보통 속음 (俗音)의 ‘갈’로 발음하지 않는다. 어느 의미에서 그 행동은 정 반대이나, 부처님이나 유마거사의 침묵과 상통하는 바가 있다

Shout!, or Katz!: A kind of soul busting exclamation to either silence the discriminating mind of the student and awaken him, or to show inexpressible ultimate truth. It is regarded as one of the characteristics of the Rinzai Sect.
Its purpose may be regarded as similar to "a great silence" with which Sakyamuni Buddha and great masters responded to the questions of the students though these two actions are dialectically opposite.