in a split second 一瞬间，霎那间 More examples: immediately in a moment at once in an instant at a word in a second right away in a blink at short notice in a twinkling of an eye instantly in one breath instantaneously in the same breath More examples: immediately in a moment at once in an instant at a word in a second right away in a blink at short notice in a twinkling of an eye instantly in one breath instantaneously in the same breath in a split second 一瞬间，霎那间