A desperado is an outlaw that you'd see in an old Western or in the Wild West. Think hip holsters, spinning guns, and a shoot-out, all with a bandanna pulled up hiding half of the face of the desperado.
You probably know the common word desperate. A hundred years ago, the word wasn’t just an adjective — it was also a noun. A desperate was someone in despair, someone in a desperate situation. And the American frontier was full of such people, people who had gone West to find gold but missed out on the mine. Desperado has the same meaning as the noun desperate, but with a Spanish influence.