The Drupal 8 module Onomasticon automatically displays the definition of taxonomy terms everywhere a term is used. However, you may want to avoid self-definition on the term's own page as its description is already visible without it.
for adding and editing abbreviations in Wysiwyg CKEditor.
The User hash allows you to create an individual hash for each user. Use it as a light-weight user identification where you do not want to use the login credentials. E.g. as an individual API Key for reading insensitive content.