ap·o·si·o·pe·sis 
(ăp′ə-sī′ə-pēsĭs)
(ăp′ə-sī′ə-pēsĭs)n. pl. ap·o·si·o·pe·ses (-sēz)
A sudden breaking off of a thought in the middle of a sentence, as though the speaker were unwilling or unable to continue.
[Late Latin aposiōpēsis, from Greek, from aposiōpān, to become silent : apo-, intensive pref.; see APO- + siōpān, to be silent (from siōpē, silence).]
ap′o·si′o·petic (-pĕtĭk) adj.