Originally coined at Apple: Forbes article.
Captured from Gitlab's famous handbook on DRI:
Apple coined the term "directly responsible individual" (DRI) to refer to the one person with whom the buck stopped on any given project. The idea is that every project is assigned a DRI who is ultimately held accountable for the success (or failure) of that project.
They likely won't be the only person working on their assigned project, but it's "up to that person to get it done or find the resources needed."
The DRI might be a manager or team leader, they might even be an executive. Or, they may themselves be individually responsible for fulfilling all the needs of their project. The selection of a DRI and their specific role will vary based on their own skillset and the requirements of their assigned task. What's most important is that they're empowered. We may disagree, commit, and disagree, but we all have to achieve results on every decision while it stands, even when if trying to have it changed.