Negative keywords are a great way to refine your keyword lists and filter out unwanted impressions for your campaigns. By excluding specific terms that aren't relevant to the services you offer, you can improve the relevance of your ads and make your campaigns more effective.
Google AdWords introduces a new way to manage negative keywords across multiple campaigns "negative keyword lists". With these lists, you'll be able to manage a group of negative keywords in your account's Control Panel and Library and associate them with multiple campaigns.
"For e.g., say you've a set of negative keywords you always add to any campaign running on the Search Network. Now, with shared lists, you can simply create a single negative keyword list and associate it with each search campaign. If there's a new negative keyword you'd like to add to all of those campaigns, just add it to your list and it'll automatically update across each campaign.
Similarly, if you create a new campaign, you can add your negative keyword list to exclude all of the necessary terms with just a few clicks," explains Google.
More Info: Help Center