
Aposiopesis

Aposiopesis (; Classical Greek: ἀποσιώπησις, "becoming silent") is a figure of speech 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-rule (—) or an ellipsis (…) may be used.
Examples.
<poem>
"Iam caelum terramque meō sine nūmine, ventī," 
"miscēre et tantās audētis tollere mōlēs?" 
"quōs ego—sed mōtōs praestat compōnere flūctūs."
</poem>
<poem>
Now, winds, you dare to embroil the sky and the earth without my approval, 
and raise up such a mass? 
You whom, I—! But it is better to settle the agitated waves.
</poem>
<poem>
"hinc mihi prima malis labes, hinc semper Vlixes"
"criminibus terrere nouis, hinc spargere uoces"
"in uulgum ambiguas et quaerere conscius arma."
"nec requieuit enim, donec Calchante ministro—"
</poem>
<poem>
This was the time when the first onslaught of ruin began for me.
Ulixes kept terrifying me with new accusations,
kept spreading ambiguous rumors among the people,
and kept looking for quarrel.
Nor did he in fact ever stop, until with the help of Calchas—
</poem>
<poem>
No, you unnatural hags,
I will have such revenges on you both,
That all the world shall— I will do such things,—
What they are, yet I know not: but they shall be
The terrors of the earth. (Shakespeare, "King Lear", II.iv)
</poem>
<poem>
"Mercutio". This is the hag, when maids lie on their backs,
 That presses them and learns them first to bear,
 Making them women of good carriage:
 This is she—
"Romeo". Peace, peace, Mercutio, peace! 
 Thou talk'st of nothing. (Shakespeare, "Romeo and Juliet", I.iv)</poem>
<poem>
"“Still it behoveth us to win the fight,”"
"Began he; “else . . . Such offered us herself . . ."
"O how I long that some one here arrive!”"
</poem>
Grammatical definition.
In syntax, an aposiopesis arises when the "if" clause (protasis) of a condition is stated without an ensuing "then" clause, or apodosis. Because an aposiopesis implies the trailing off of thought, it is never directly followed by a period, which would effectively result in four consecutive dots.