Something that is being progressively modified, and improved over time. Most usually used to suggest that it's happening at a rate more slowly than desired.
"How is the renovation on your house coming along?"
"It's a work in progress."
"You've been spending a lot of time at the gym. How is your fitness coming along?"
"I'm a work in progress."
Something that has the appearance of something regular or ordinary, but robotic in action, having to do what it is programmed to do, not allowed free thought or action.
Also title of famous book and movie having much to do with this topic.