expression, noun-modifying (irregular)
insane; crazy; nuts; out of one's mind
Used to describe someone whose thinking or behavior is irrational or mentally unstable. Often carries a strong, informal, and somewhat derogatory tone. Compare with 頭がおかしい, which is a full clause rather than a prenominal modifier.
See also: 頭がおかしい
彼は頭のおかしい人だと思われている。
He is thought to be a crazy person.
そんな頭のおかしい計画に賛成できるわけがない。
There's no way I can agree to such an insane plan.
Phrase composed of 頭 (head/mind) + の (possessive particle) + おかしい (strange/funny). Literally 'of a strange head', it functions as a prenominal adjective meaning 'crazy' or 'insane'.