What is threat as an verb?

'Threat', of course. The litmus tests for a noun: can it take an article, adjective or possessive (the threat; the dire threat, the threat's dissuasive power); can it be used as the subject or object of a sentence? (the threat was taken seriously; they perceived a threat in his tone), can it take a relative clause modifier? (the threat that she would fail was an incentive)