An upcoming feature in Word 365 for Windows (commercial editions) will be able to detect and define acronyms.
When Word ‘sees’ an acronym it will try to show a definition based on it’s context in the document and how other people use the same acronym in the organization.
Source: Microsoft plus some extra edits
That’s why this feature is only in commercial releases of Office 365. It relies on access to a pool of documents within the organization, saved in Microsoft’s cloud services.
Using an organizations documents as a source means that ‘in-house’ shortcuts (like acronyms for departments, products or positions) can appear in Word.
It’s possible the feature is boosted by a common pool of acronyms like AI in the Microsoft example above.
It’s at References | Insights | Acronyms in commercial versions of Office 365. An E3 or E5 Office SKU, Exchange hosted in North America with language set to US English.
Acronyms is in Office Insiders v 1908 Build 11901.20038 and later.