A prism splits white light into colours, so it is read as seeing many sides of one thing. Dreaming of it is often taken as gaining new perspective on something you thought was simple.
Where in your waking life have you met something like this lately?
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.