Z-M is right and my take is that it refers to a self-entitled, egotistical person (can be male as well) that believes the world revolves around only them and somehow is able to somehow 'prove' it by a continuous bullying rant at high volume with very little reference to common sense. If only the power of their voices could be harnessed for the common good.
I think if they are blonde it has come out of a bottle. They are usually on their way to 'do' lunch.
They usually choose to drive huge SUV cars, then struggle to park them.