A telesales term for the person who will prevent you from reaching your target (sale). In business sales it will usually be the personal assistant and for a household sale it will be a concerned relative.

In the case of business related sales the trick to get around the gatekeeper is to convince them you are a legitimate caller rather than someone trying to make a sale. I believe it's called "having an air of authority about you".

Good luck with household sales as most people aren't required to be "polite" in their own homes, whereas a personal assistant has to.