A woman who is, at her very core, stupid and/or ignorant. Normally this word is used toward women who are over forty. It is not often used toward younger women or women in their teens. "Dumb" refers to a person who cannot speak, and most dumb beavers talk far too much, so the definition is not completely accurate, in a literal sense. Still, when you say "dumb beaver," everybody knows exactly what you mean.
1. While riding my Harley, this dumb beaver pulled out in front of me. She must have been late for her hair appointment!
2. It would have been nice to actually get the questions answered, but the dumb beaver on the phone was too ignorant to be helpful.