crazy deed; act of sheer madness; the height of madness
Colloquial expression used to describe an action or situation that is so extreme or irrational that it seems insane.
Making a plan like this is sheer madness.
There's no way to describe him betting his entire fortune other than as an act of madness.
沙汰 alone means 'affair' or 'matter', often used in formal contexts like 裁判沙汰 (court case). 狂気の沙汰 is a fixed phrase meaning 'an insane affair'.
狂気 means 'madness' or 'insanity' as a noun. 狂気の沙汰 uses it attributively to describe an extreme deed.
Standard kanji spelling.
Kana spelling of 沙汰; common in casual writing.
Compound of 狂気 (madness) + の (possessive particle) + 沙汰 (affair, matter). The phrase literally means 'an affair of madness' and is used idiomatically to express extreme irrationality.