harebrain

Noun

A person who lacks good sense; One who is foolish and reckless.

Japanese Meaning

愚かで無謀な人 / 判断力に欠けた人 / 軽率な人

Only a harebrain would attempt to fix the electrical wiring without shutting off the power.

電源を切らずに電気配線を修理しようとするのは、分別のない人だけだ。

Sense（1）

A person who lacks good sense; One who is foolish and reckless.

...rash harebrain treating matters that require age and gravity;

harebrains

（ plural ）