"a split second" in Chinese (Simplified)
一瞬间一刹那
Definition
极短的时间；用来形容事情几乎立刻或非常快地发生。
Usage Notes (Chinese (Simplified))
这是非正式的表达，常和“in”搭配（如'in a split second'），用来强调事情发生得非常快，类似于“一瞬间”或“一眨眼”。不用于正式或技术性场合。
Examples
Everything changed in a split second.
一切在**一瞬间**改变了。
He reacted in a split second to catch the ball.
他在**一刹那**就抓住了球。
The answer came to me in a split second.
答案在**一瞬间**出现在我脑海里。
She disappeared in a split second after the door opened.
门一开，她**一瞬间**就消失了。
Trust can be broken in a split second if you're not careful.
如果不小心，信任**一瞬间**就会破裂。
Don't worry, that pain will be gone in a split second.
别担心，那个疼痛会在**一刹那**消失。