noun or participle which takes 'suru', intransitive verb, noun
clearing one's mind of all worldly thoughts; emptying one's mind
yojijukugo (four-character idiom)
A yojijukugo used in Zen-like contexts to describe a state of mental detachment from worldly concerns. Often used in the set phrase 心頭滅却すれば火もまた涼し (if you clear your mind, even fire feels cool).