From V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016) :
XML
eXtensible Markup Language (WWW, XML, W3C)
From The Free On-line Dictionary of Computing (30 December 2018) :
Extensible Markup Language
XML
(XML) An initiative from the W3C defining
an "extremely simple" dialect of SGML suitable for use on
the web.
http://w3.org/XML/)">(http://w3.org/XML/).
[Relationship to the XSL forthcoming subset of DSSSL?]
(1997-11-20)