To dream that you are Dumb signifies your failure to induce others to see your perspective."

To dream that you are dumb denotes your inability to persuade others to see your point of view.

To dream of being dumb, indicates your inability to persuade others into your mode of thinking, and using them for your profit by your glibness of tongue. To the dumb, it denotes false friends.

If you see yourself in a dream dumb - it means that somehow your act you drop so much dignity that long then can not be justified either in their or in the eyes of others.