Disavow definition in SEO means to discard harmful links pointing to your site. If you believe your site's ranking is being damaged by low-quality links you do not control. You can ask Google not to take them into account when assessing your site by disavowing your backlinks.

The first step in disavowing links is to identify the links that you want to disavow. This can be done using a tool such as Google Search Console or Ahrefs. These tools allow you to see all the links pointing to your website and can help you identify any links that may be harmful to your website's rankings.

A domain that has been disavowed, meaning that all links originating from it will be ignored, such as domain:spammy-example.com. You can also disavow subdomains in the same format as the domain format, such as domain:subexample.spammy-example.com.