KOed
mod. “knocked out.” (Initialism. Originally from boxing.)Wilbur was KOed and got a cut over his eye.He stayed KOed for about two minutes.
out cold
mod. unconscious.Paul was out cold when we found him.Who knocked him out cold?
out like a light
mod. unconscious or sleeping soundly.I fell and hit my head. I was out like a light for two minutes, they tell me.I closed my eyes and was out like a light in no time at all.
see stars
tr. to be (knocked) unconscious.If you talk to me like that again, you'll be seeing stars.I saw stars for a few seconds, and then someone threw cold water in my face.