The ability to converse, written or verbally, in a powerful, persuasive way, particularly using examples and figures of speech to make a case.
A context where I used this skill:
I was talking to a release manager at lunch. The project was, for the company, pretty big -‐‑ perhaps 200 person-‐‑years and 24 calendar months, perhaps a bit larger. The team was trying scrum, but the 'test' process was spiraling out of control, or at least, was in danger of spiraling. I took my spoon and waved it around like a magic wand, and said "Say I have a magic wand that makes testing free. And we've got buggy software. So I wave my wand and tell you the status. You get a bunch of bug reports. The programmers fix the bugs. I wave my wand again, we now have less bugs (we hope) and we fix. Then I wave my wand again ... we've made the test process free, but we've still got the fixing process. Plus figuring what to build and building haven't experienced any drop in cost. So the overall project cost savings might be, what? 10 percent? And while I do have my moment, I doubt I'll ever be able to make testing free. Which means if we put me on the project, we'll have, at most, realistically, a 5% decrease in cost, or a moderate increase in throughput. I think you want more than that. To do that, we'll have to work on the whole process -‐‑ identify bottlenecks and waste, prevent failures and rework, and shift resources to alleviate the bottleneck. If we can do that, we can often see increases in throughput more like 50% -‐‑ and that accordion effect, where test is working on something that 'ended' 3 iterations ago? That can go away."
I got the contract, and the opportunity to try my ideas on the whole process -‐‑ not just in test.
How I'd recommend someone learn this skill:
Read great literature. Yes, Aristotle and Plato, but also Shakespeare, Huxley (Brave New World), and even Ayn Rand (Atlas Shrugged). You don't have to agree with Rand, but do study what makes her so persuasive.
Speak publicly, even in small groups, to make a case for something you want, and ask for feedback on how you do. Start small and build up.
Remember to be friendly, strong and use some arguments (but still be positive so no name calling ). Another way to improve this skill is in debates.
This skill is similar to Eloquence, Communicating Risks , which you might think of as a special kind of rhetoric.
Your Brain at Work, by David Rock, contains a list of social and emotional triggers to voice when trying to convince someone of something.