When you dream vacuum means: There are two possible ways to define a vacuum as a symbol of the dream. Another way to look at them is as representations of cleaning out or removing items that are not part of the subconscious. The symbol of the subconscious mind, or the psyche of the dreamer, are houses. It can be used to reflect the cleaning of clutter in the mind. It is the same as cleaning up spiders in your dream. This can also be interpreted to mean removing any negative thoughts from your head. Vacuuming in your dreams is, basically speaking, a positive symbol which metaphorically purges a negative part of you that may have not been noticed before.
(in Dream Dictionary)