vi to use threats, or menaces; also, to have a threatening appearance.
2. threaten ·vt to exhibit the appearance of (something evil or unpleasant) as approaching; to indicate as impending; to announce the conditional infliction of; as, to threaten war; to threaten death.
3. threaten ·vt to utter threats against; to menace; to inspire with apprehension; to alarm, or attempt to alarm, as with the promise of something evil or disagreeable; to warn.