Did you ever ask for a more compact way to express something in your favorite programming language? Say hello to DSL (Domain Specific Language). A DSL is a slang, a compact way to say what you want. When two astronauts talk, they use slang. They need to get information across and presto. "Over" instead of "I'll now clear the frequency so you can start talking." And when these guys do it, there's no reason for us not to.
Here is an artical on Java World which gives some nice examples how to create a slang in Java and in Groovy. Pizza-lovers of the world, eat your heart out.