1. a declaration of an intention or determination to inflict punishment, injury, etc., in retaliation for, or conditionally upon, some action or course; menace:

He confessed under the threat of imprisonment.
2. an indication or warning of probable trouble:

The threat of a storm was in the air.
3. a person or thing that threatens.

Verb (used with or without object)

4. Archaic. to threaten.