Dead to the World: Origin and Meaning

If somebody’s fast asleep and completely unaware of what is happening around them, he or she’s dead to the world.

It means “fast asleep”. It looks, to the world, that the person is dead, because they are so deep in sleep that they are not being disturbed by any noise around them.

Simon: Do you realise that we have been together for precisely 3 months, 2 weeks, 4 days, and 6 hours?
Jane: It’s not really a long time.
Simon: No, not if you compare it with say, the Queen, she’s been married for ages,. Like 60 years or something, but it’s something at least.
Jane: True. Did you know you move about a lot when you’re asleep?
Simon: Do I?
Jane: And you steal the entire duvet plus the fact you snore.
Simon: Snore? Like an old man you mean.
Jane: Then of course there is the talking in the sleep.
Simon: What do I talk about?
Jane: We are not going to be together much longer unless you change your sleeping habits.
Simon: What do I talk about?
Jane: I don’t know, but it always seems to involve a girl called Mandy.
Simon: I don’t know a girl called Mandy.
Jane: Well, in your dreams you do.
Simon: How can I change my sleeping habits when I’m dead to the world?
Jane: You can stop talking to Mandy for a start.