about a dream about a dream about a dream... ad infinitum
. Alternatively, a dream in which you wake up
from a dream in which you wake up from a dream... etc
The latter actually happened to the author of this node a few days ago. Basically, I woke up from an afternoon nap, really thirsty, so I reached for the bottle of water which I conveniently keep within reach... only to wake up, really thirsty, so I reached for the bottle of water... you get the picture.
This happened at least 8 times within the dream... however, after the second time, I noticed that I was stuck within a recursive dream loop, and started to panic. When I did finally wake up, for real, I spent the first 10 or so minutes in extreme wariness, expecting another repetition of the loop at any moment.
It's things like these which really make you wonder if that "reality" thing is really all that it's hyped up to be.
See also: The Matrix is going down for a reboot in 5 minutes: all users, please save your data and log out.