The Grim Reaper is read as the symbol of endings and transformation. Seeing him is not a death notice; tradition takes it as a sign that something is closing so something else can begin.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.