Jonathan Bardo

Note: This plugin only works with WordPress 4.2 or higher
This plugin will enable the site administrator to easily create an admin message present on all pages. The admin has the option to let the user dismiss the message for the duration of his session.

Admin User Message

This does just what I want. Thanks for making it. :)
It's definitely better than https://wordpress.org/plugins/admin-screen-messages
You might want to also tag it as:
https://wordpress.org/plugins/tags/admin-message



Perfect

Add message to users of your site. Choose wheter they can dismiss it or not.

Nicolas Bouliane

This plugin will display a small ??? icon that links to either the definition or the translation of the word. The plugin is a no-brainer to use: [define:dog] will define the word ?dog? and [en2fr:dog] will translate the word ?dog? from english to french. [wikies:dog] will show the Wikipedia article for the given word in spanish (es). Dictionary.com is used to define words, as it has definitions for technical terms too. Translation works with Google’s translation engine.
For a list of 2-letter language code, see here: http://reference.sitepoint.com/html/lang-codes

Word Definition Links

Inserts subtle links to definitions, Wiki articles and translations of words in multiple languages using short tags.

Admin User Message vs Word Definition Links