Twitter is testing the "soft block" feature
Twitter has begun testing the first of its proposed suite of new privacy tools: the ability to remove a follower without blocking them. The remove follower feature is currently being tested on the web and appears to canonize the concept of "soft block" as an official Twitter tool.
Based on the tweet announcing the test, you can remove followers from the follower list on your profile page. Just click on the three-dot menu next to a follower's name, click "Remove Follower" and their tweets will no longer automatically appear on your timeline.
This is different from blocking someone, which prevents them from viewing your tweets and sending you direct messages (and prevents you from doing the same to them). The new remove Twitter followers feature is more of a remote unfollow button, a smoother way to create some distance between yourself and someone else on Twitter.
Previously, to get someone to stop following you without their knowledge, you could do a "soft block", which is when you manually lock and unlock someone. Followers you delete have to re-follow you to see your tweets on their timeline, and if you have protected tweets (also known as private tweets, only visible to your followers), they will need your approval to become a follower again.
Testing functionality similar to an official Twitter feature is an admission that it could probably be easier and that people could benefit from it. It is also yet another case in which Twitter makes the habits of its user's official functions, such as @reply, hashtag and retweet.
An even better solution might be more granular control over who can see your tweets at the time of tweet conception (Twitter is considering an Instagram-like "Close Friends" option), but for now, you'll need to delete your list of followers easily and quietly.