MP5
From WoWWiki
MP5 (also known as MP/5) is a shortened term for the item bonus "Restores X mana per 5 sec." Although the number given is based on 5 second intervals, the effect triggers every 2 seconds. For example, an item that grants 10 mana per 5 sec restores 4 mana every tick. See the Mana regeneration article for the detailed mechanics of spirit and mp5 based regeneration.
