I've been thinking about this for a while. I fancy myself a scientist, which means I use the Scientific Method to figure things out. So I make a hypothesis, and try like crazy to falsify it, and at the end maybe there's some interesting not-yet-falsified ideas.
I train myself in all sorts of science, I keep real genuine article scientists as friends and compatriots. But y'know, I probably wouldn't be called a Scientist by the vast majority of people in this day and age.
So I started thinking. What is someone who does science who doesn't have impressive scientific credentials? And I came to - a Cowboy Scientist.
Cowboy Science is trying to figure out how things for practical reasons or for curiosity, not for academic or institutional prestige.
A rancher who tries to figure out what the best mix of water and grazing and movement for his cattle by takes notes, making a guess at what'll work, and testing that guess - he's doing science. But no one would call him a Scientist with a capital S.
But that's science, y'know. That's the nice thing about science - it's defined by doing it. You can put on a fancy hat and get a fancy piece of paper and not be doing science, and you could be out on horseback paying attention to your cattle and doing science.
I'd say the defining feature of cowboy science is trying to scratch a personal itch. You don't get the credentials, but then, it seems a lot of the interesting breakthroughs come from cowboy scientists who aren't as concerned with establishments and credentials and academic prestige. Years later we look at them as model scientists, but in their lifetime they're seen as sort of rogue not-serious cowboys. But y'know? I like that. Cowboy science it is.
Edit: A good comment left by Alessandro:
Well, I think there is one point lacking (well maybe not expressed): the fact that a scientist has a community around him that checks his findings.
I think that what a lone (ranger) thinker sometimes lacks (and maybe feel the need of) is a community of like-minded people to crash with and to be checked by.
Maybe the cowboys just talk about the cows at the nearest saloon, I don't know, but thinking in solitude may cause lots of errors.