Webster's Revised Unabridged Dictionary · 1913

Threaten

Threaten , transitive verb

[Old English þretenen. See Threat, transitive verb]

1.
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.
Let us straitly threaten them, that they speak henceforth to no man in this name. — Acts iv. 17
2.
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. — Milton
The skies look grimly And threaten present blusters. — Shakespeare
By turns put on the suppliant and the lord: Threatened this moment, and the next implored. — Prior
Of the sharp ax Regardless, that o'er his devoted head Hangs menacing. — Somerville

Threaten , intransitive verb

To use threats, or menaces; also, to have a threatening appearance.
Though the seas threaten, they are merciful. — Shakespeare