Definition
to render oneself unconscious, typically by striking the head
晕倒（常因碰撞头部）
Be careful of that threshold, or you might knock yourself out by accidentally hitting your head.
小心那个门槛，否则你可能会不小心撞到头，让自己失去知觉。
While playing with his friends, he accidentally fell to the ground and knocked himself out.
和朋友玩耍时，他不小心摔倒在地上，让自己失去了知觉。
If you're not careful and hit your head, you could knock yourself out.
如果你不小心撞到头，可能会让自己失去知觉。
to exhaust oneself to the point of illness
累垮
He pushed himself to run thirty kilometers in the marathon, and in the end, he really knocked himself out.
他让自己在马拉松中跑了三十公里，最后真的把自己累垮了。
If you work all day without a break, you'll soon knock yourself out.
如果你整天工作不休息，很快就会把自己累垮。
She studied hard for the exam and ended up knocking herself out.
她为考试努力学习，结果把自己累垮了。