形容词

1. 精神错乱的;精神失常的;疯狂的
Someone who is insane has a mind that does not work in a normal way, with the result that their behaviour is very strange.

2. 蠢极的;荒唐的
If you describe a decision or action as insane, you think it is very foolish or excessive.

1. afflicted with or characteristic of mental derangement

e.g. was declared insane
insane laughter

2. very foolish

e.g. harebrained ideas
took insane risks behind the wheel
a completely mad scheme to build a bridge between two mountains

Synonym: harebrainedmad