1. 威胁;恐吓
    If a person threatens to do something unpleasant to you, or if they threaten you, they say or imply that they will do something unpleasant to you, especially if you do not do what they want.

    e.g. He said army officers had threatened to destroy the town...
           他说陆军军官们曾威胁要摧毁那座小镇。
    e.g. He tied her up and threatened her with a six-inch knife...
           他把她捆起来，拿着一把 6 英寸长的刀子威胁她。

2. 危害到;威胁到
    If something or someone threatens a person or thing, they are likely to harm that person or thing.

    e.g. The newcomers directly threaten the livelihood of the established workers...
           新来的工人直接威胁到老工人的饭碗。
    e.g. The unity of our society is threatened by troublesome and restless minorities...
           我们社会的团结遭到了一小撮滋扰生事、不安分守己的群体的威胁。

3. (坏事)可能发生，将要发生
    If something unpleasant threatens to happen, it seems likely to happen.

    e.g. The fighting is threatening to turn into full-scale war...
           这场战斗有可能会演变为全面的战争。
    e.g. Plants must be covered with a leaf-mould or similarly protected if frost threatens.
           如果霜冻来临，植物必须盖上腐叶土或用类似方法加以保护。

4. see also: threatened;threatening