0 used to refer to the unpleasant feeling that some people have when they see robots (= machines that can carry out actions automatically), or pictures of a human being created by a computer, that appear very similar to a living human:
The development of humanoid robots has been hampered by what some roboticists call the "uncanny valley".
They're always trying to make humans on the screen look more realistic, and there's this phenomenon called the "uncanny valley" where it becomes a little creepy.
We witnessed the impact of the Uncanny Valley at the movie theatres in 2004.
The astonishing character animation suggests the uncanny valley might have been successfully crossed.
