1. Robust or complex aspects or characteristics that are not easily noticed or readily apparent. While the film makes no apologies for its graphic, over-the-top violence, there are hidden depths to the characters and their motivations that make this much more than just some schlocky B movie. If you get to know him, you come to realize that his ironic, apathetic public demeanor is on show to hide hidden depths of anguish and insecurity.

2. A place or part of something that is hidden away and requires a lot of searching or prior knowledge. I'm hesitant to give my child access to the internet, knowing full well what horrible things lie in its hidden depths. Astronomers have discovered a new solar system in the hidden depths of space.