If you describe behaviour as foolhardy, you disapprove of it because it is extremely risky.
例句
When he tested an early vaccine on himself, some described the act as foolhardy...当他在自己身上试验还处在初级阶段的疫苗时，有些人说他的行为是蛮干。It was foolhardy to have refused.拒绝是极不明智的。