It can mean in a very deep sleep, or it can mean unconscious. I actually found myself

using this the other day describing how well I was sleeping. I didn't hear the sirens last

night, I was out like a light. However, I've also used it before for having been unconscious.

I was chopping vegetables one day not too long ago and I cut off the very end of my

thumb. And I ended up at the ER. And when they took the bandage off of my thumb, I immediately

passed out. I was out like a light. This phrase begins with the 'ow' as in 'now' diphthong,

ow, ow, and it then has the T. It's a final T, so you might hear it as a stop T, out,

out, or you might hear it lightly released, out, out. Like, the L consonant sound and

the 'ai' as in 'buy' diphthong. Out li-, out li-, kk. The K consonant sound -- out like,

out like, a. The schwa. Out like a. Out like a. And finally, light, the L consonant sound,

the 'ai' as in 'buy' diphthong, and again a final T. So, it might be stopped, or it

might be released. Light or light. You'll notice the words 'out' and 'light' are the

stressed words here. Out like a light. Out like a light. I was out like a light.