[programming] Acronym for Extensible Style Language Transformations. A language for transforming the tagged content in an XML document into an output document with another format. An XSL style sheet contains the XSLT code that defines each transformation to be applied. Transforming a document requires the original XML document, an XSL document containing XSLT code, and an XSLT processor (parser) to execute the transformations. The W3C maintains the XSLT standard.