Blacklist

The blacklist is a bidirectional tool in order to make your giveaways unaccessable for the chosen person and vice versa.

How does a blacklist work?

On user profiles, you'll see a button that has a circle icon with a slash through it. Clicking this button will add the user to your blacklist. This means the user will no longer see your giveaways on the homepage, and they will not be able to view or enter your giveaways from this point forward. If the user entered one of your giveaways prior to being blacklisted, their entry still remains valid.

From FAQ... which is exactly for most common questions... little pro tip: such FAQ pages are all over the internet.