A vat is a large vessel where something ferments or is mixed, and dream books read it as a slow transformation in progress. Falling into one can stand for being swallowed by a situation.
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.