A swarm is read as many small pressures acting as one — overwhelming in number, hard to fight one by one, and sometimes simply a group on the move.
When this appeared in your dream, what were you feeling?
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.