What is samadhi?

Your book ‘Mystics Musings’, which I read many years ago when I lost my younger brother. It was a great tragedy in the family and something that I was finding difficult to cope with. It gave me a great amount of courage and made me feel much better. Also it talked a lot about spirits, it talked a lot about life being a continuous process. In that, you write about when you and your wife, everybody was constructing the Dhyanalinga. And you talk about how a thread of life, grasp of life, something to that effect, became very fragile. When she could not hold onto it and she passed away. What exactly did you mean by that?