He is dangerously ill.

他病得很重。

《柯林斯英汉双解大词典》

He rode away, and when he reached his father, the latter was dangerously ill, and near his death.

他骑马走了，当他到达他的父亲身边时，他的父亲已经病得很重，快要死了。

youdao

Can you imagine how you would feel if you fell dangerously ill and could not reach or call a doctor?

你能想像，如果你得了很严重的病并且不能到医生那或打电话给医生时，你是怎样的感受吗？

youdao

"We think that you ought to have a background check at gun shows. We think you ought to have a background check so that people who are dangerously mentally ill aren't getting their hands on guns."

VOA: standard.2010.04.19

When Mr Yeltsin fell dangerously ill and underwent a heart bypass operation, Mr Chubais held the machinery of government together.

ECONOMIST: The humbling of Chubais | The

An unheralded weekend session of parliament lifted his immunity and he was put in jail, where he remains, despite doctors' pleas that he is dangerously ill.

ECONOMIST: Egypt

Have personnel trained to respond and intervene, possibly to incarcerate the dangerously mentally ill.

FORBES: Searching For Hard Data On Guns And Violence