A cloister is a covered walk around a closed garden. Dream books read it as protected reflection: a sheltered place in the mind where thoughts can go round slowly without interruption.
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.