Hi Paul,
I’m using Living Documentation in the sense of Cyrille Martraire’s book Living Documentation https://www.amazon.co.uk/Living-Documentation-Cyrille-Martraire/dp/0134689321
Essentially, whenever a system changes, the documentation should update as well. Ideally in a self-documenting fashion as explored here: https://medium.com/nick-tune-tech-strategy-blog/self-documenting-architecture-80c8c2429cb8