1. It's a culture where dev and ops work together (as per TFA);
2. It is the application of software engineering practises (such as version control and test automation) to ops.
I prefer the second definition because it's the only one that's got anything to do with new developments in infrastructure-as-code and isn't just a new name for what competent teams were always doing anyway.
More unfortunately, it is also a long ramp up time to bring sysadmins who don't know programming up to speed on software development. I'd like to know what others are doing to quickly build a devops team if they are doing that, other than "find highly-skilled senior sysadmins who already know software development", because that's my go-to approach for the time being, as it is way faster to teach someone like that Ansible if they already use Chef, for example, than pick up sysadmins or devs and cross-train them into the other field.
Not everyone is the pitcher, the catcher, the first baseman, etc. We specialize because that's how humans work best together. Everyone should not need to know how to do everything.
Developers must work with operations - of course. The way and the what developers build must be able to be deployed in an agile manner. But, that does not mean that developers must become operations engineers as well. Leave that to the specialists in that role.
In soccer, this argument holds less weight. I prefer soccer.
That's interesting. I see that the opposite way: weren't competent ops teams already doing the things you listed in #2? Does keeping up with new developments in operations tooling need a new name? Shouldn't that just be part of doing ops well?