to tell someone that you will kill or hurt them or cause problems if they do not do what you want

They threatened the shopkeeper with a gun. 他们用枪威胁店主。

[ + to infinitive ] They threatened to kill him unless he did as they asked. 他们威胁要杀他，除非他按他们说的去做。

to be likely to cause harm or damage to something or someone

Changing patterns of agriculture are threatening the countryside. 农业模式的变化可能会对农村造成破坏。

If something bad threatens to happen, it is likely to happen.

Look at those clouds! There's a storm threatening. 看那些云！暴风雨要来了。