Aposiopesis (pronounced /ˌæpəsaɪ.əˈpiːsɪs/ from Classical Greek, ἀποσιώπησις, “becoming silent”) is a rhetorical device wherein a sentence is deliberately broken off and left unfinished, the ending to be supplied by the imagination, giving an impression of unwillingness or inability to continue. An example would be the threat “Get out, or else—!” This device often portrays its users as overcome with passion (fear, anger, excitement) or modesty. To mark the occurrence of aposiopesis with punctuation an em dash or an ellipsis may be used.

A classical example of aposiopesis in Virgil occurs in Aeneid 2.100. Sinon, the Greek who is posing as a traitor to deceive the Trojans into accepting the Trojan Horse within their city wall, tells about how Ulixes spread false rumors at Sinon’s expense. Indeed, Ulixes does not stop his malicious gossiping until he causes Sinon’s ruin with the help of the seer Calchas. The whole story is a lie that Sinon tells with consummate artistry in order to convince the Trojans that he deserted the Greeks to escape Ulixes’s enmity. To ensure the effect of his elaborate lie, Sinon at one point leaves a crucial statement unfinished (Aen. 2.97-100):

via Aposiopesis – Wikipedia, the free encyclopedia.