"Lean Thinking" is a process management philosophy, and is often associated with Toyota Production System.

I first heard of this via my friend Jane, who is applying this in a healthcare setting.

It might sound a bit strange using a manufacturing philosophy (where the business is all about production lines and making widgets) to a hospital (which normally deals with lots of people with various health problems). However I've heard they've been applying the lean principles with some positive effects to things like waiting times for people in emergency and also improving how patients are moved through the hospital - the "patient journey".

And so it isn't just in healthcare that a manufacturing philosophy is being used - we now have Lean Software Engineering too. I'm not an expert on all the details, but it does seem to relate to a lot of the Agile practices that are becoming more popular now.