DevOps is a philosophy.

The roots of DevOps arose directly out of the continuous delivery with the Flickr presentation in 2009 on 10 deploys per day. As Gartner puts it

DevOps — Not a Market, but a Tool-Centric Philosophy That Supports a Continuous Delivery Value Chain

- Gartner

Gartner nails it - DevOps is doing what it takes to a provide continuous delivery value chain. Unfortunately many people want to keep DevOps so open ended that they risk dooming the movement.  The DevOps movement can succeed once there is a stake in the ground with a clear definition to rally around. DevOps is defined as the tools and culture that provide a continuous delivery value chain. From this short definition all the tools, groups required, cultural changes, processes and methods like feedback loops can be expanded upon.