Definition:
The phrase "knocked out" usually means to be made unconscious, often because of a strong hit or blow to the head. Imagine someone getting hit hard and then falling down, unable to wake up for a while.
As an Adjective: You can use "knocked out" to describe someone who is unconscious because of a blow.
In Other Contexts: "Knocked out" can also be used informally to mean feeling extremely tired or exhausted.
In a more figurative sense, "knocked out" can describe being very impressed or amazed by something. - Example: "I was knocked out by the performance of the band last night."
For Unconscious:
For Tired:
"Knocked out" is a versatile phrase that can mean being unconscious from a hit, feeling very tired, or feeling impressed by something.