You've been able to mute accounts to block tweets, however, twitter is rolling out a new addition which means you can now mute keywords and phrases, or conversations. This might be particularly helpful if there is abusive or hateful messages on your time-line. It doesn't stop the abuse, but it allows you to hide it from view.
On top of that new ability, twitter has said it's making it easier to report abusive and hateful messages, not only on your own account, but if you've seen it on other time-lines and feeds.
Once you've reported that you'll want to know that twitter has trained its team and improved its internal systems to better handle reports.