What is a figure of speech in which the speaker breaks off suddenly, as if unwilling or unable to state what was in his mind; as, "I declare to you that his conduct -- but I can not speak of that, here." called?

aposiopesis — A figure of speech in which the speaker breaks off suddenly, as if unwilling or unable to state what was in his mind; as, "I declare to you that his conduct -- but I can not speak of that, here.". (Webster's 1913.)