This wiki has a Terminology page where you can add/edit glossary terms. Thanks to the mw:Extension:Lingo, these terms are then visually expanded by 'tooltips' wherever they occur in the content. For example, the acronyms API and GNHLUG used in this sentence are decorated by the Lingo extension due to their definitions in the Terminology page.
If you see an acronym on this wiki, and it doesn't have a tooltip, then fix it by adding it to the Terminology page.
There can actually be multiple such pages in case your organization or content structure would work better with multiple glossaries.