The <acronym> tag defines an acronym.

By marking up acronyms you can give useful information to browsers, spellcheckers, screen readers, translation systems and search-engines.

This tag is not supported in HTML5, use the <abbr> tag instead.

Example Code:
Most web page editors are <acronym title="What You See Is What You Get">WYSIWYG</acronym>
Most web page editors are WYSIWYG