Salesforce BlacklistedConsumer Metadata contains the Connected Apps that are blocked or inaccessible to the Users.

1. Go to Connected Apps OAuth Usage in Salesforce Setup.

2. Block the Connected App by clicking the Block button.

3. The Unblock button will be displayed to unblock the Connected Apps.

Sample package.xml to retrieve:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Package xmlns="http://soap.sforce.com/2006/04/metadata">
    <types>
        <members>*</members>
        <name>BlacklistedConsumer</name>
    </types>
    <version>59.0</version>
</Package>

Following exception is thrown when the Blocked Connected App is used.

{
    "error": "app_blocked",
    "error_description": "this app is blocked by admin"
}