Sass (Syntactically Awesome Stylesheets) is a dynamic cascading style sheet generation language.
Sass is a CSS preprocessor. It is a description language compiled in CSS. SassScript is a scripting language that can be used inside Sass code. Two syntaxes exist. The original syntax, called "indented syntax", is close to Haml. The new syntax is called SCSS. It has a formalism close to CSS.