Aposiopesis is a sudden break in speech or a poem's line of thought before the sentence is finished. The pause suggests that the speaker cannot, will not, or does not need to say the rest, and the missing words are meant to be understood from context. In poetry, it is often marked by a dash or ellipsis.
The term was coined by Otto Jespersen, for the rhetorical device by which the speaker or writer deliberately stops short and leaves something unexpressed, but yet obvious, to be supplied by the imagination, giving the impression that she is unwilling or unable to continue. It often portrays being overcome with passion (fear, anger, excitement) or modesty. The ellipsis or dash is used.
Example
You think I'll beg for mercy, but I would rather-
No. Let the silence answer for me.
Quos ego—!
[n] breaking off in the middle of a sentence (as by writers of realistic conversations)