The Collaborative International Dictionary of English v.0.48:

Threat \Threat\ (thr[e^]t), n. [AS. [thorn]re['a]t, akin to
   [=a][thorn]re['o]tan to vex, G. verdriessen, OHG. irdriozan,
   Icel. [thorn]rj[=o]ta to fail, want, lack, Goth.
   us[thorn]riutan to vex, to trouble, Russ. trudite to impose a
   task, irritate, vex, L. trudere to push. Cf. Abstruse,
   Intrude, Obstrude, Protrude.]
   The expression of an intention to inflict evil or injury on
   another; the declaration of an evil, loss, or pain to come;
   menace; threatening; denunciation.
   [1913 Webster]

         There is no terror, Cassius, in your threats. --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Threat \Threat\, v. t. & i. [OE. [thorn]reten, AS.
   [thorn]re['a]tian. See Threat, n.]
   To threaten. [Obs. or Poetic] --Shak.
   [1913 Webster]

         Of all his threating reck not a mite.    --Chaucer.
   [1913 Webster]

         Our dreaded admiral from far they threat. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

threat
    n 1: something that is a source of danger; "earthquakes are a
         constant threat in Japan" [syn: menace, threat]
    2: a warning that something unpleasant is imminent; "they were
       under threat of arrest"
    3: declaration of an intention or a determination to inflict
       harm on another; "his threat to kill me was quite explicit"
    4: a person who inspires fear or dread; "he was the terror of
       the neighborhood" [syn: terror, scourge, threat]