Glossary
To use this feature, please enable the PimcoreGlossaryBundle in your bundle.php file and install it accordingly with the following command:
bin/console pimcore:bundle:install PimcoreGlossaryBundle
General
The glossary module is a powerful tool making internal linking easy and smart. In a special editor you can define your terms which are replaced automatically with a link to the defined page.
But the glossary is not only useful for internal linking, it's also perfect for explaining abbreviations.
How it Works
Open the glossary editor 
Tools -> Glossary and define some terms.
Then you have to define one or more regions in your views, telling the glossary where you want it to replace your terms.
{% apply pimcore_glossary %}
<div>
{{ pimcore_wysiwyg('content', { height: 200 }) }}
</div>
{% endapply %}
Now the output of the WYSIWYG field will look like this.
And the HTML-markup will look like, below.
<p>
<abbr title="Hypertext Preprocessor">PHP</abbr> is a widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages. For this purpose, <abbr title="Hypertext Preprocessor">PHP</abbr> code is embedded into the HTML source document and interpreted by a web server with a <abbr title="Hypertext Preprocessor">PHP</abbr> processor module, which generates the web page document. As a general-purpose programming language, <abbr title="Hypertext Preprocessor">PHP</abbr> code is processed by an interpreter application in command-line mode performing desired operating system operations and producing program output on its standard output channel. It may also function as a graphical application. <abbr title="Hypertext Preprocessor">PHP</abbr> is available as a processor for most modern web servers and as standalone interpreter on most operating systems and computing platforms. You can <a href="https://www.php.net/">download</a> it free at php.net.
</p>
Note
Since the glossary depends on languages you'll have to register a language first.