Board Thread:Help Desk/@comment-108.235.34.45-20130126144844/@comment-3157150-20130210234708

It's referred to as a prefix more so than anything. There is a huge range of prefixes ranging from (but not limited to) Terrible to Legendary, Slow to Unreal, Ignorant to Mythical, and that's just for Melee, Ranged and Magic weapons. There are also prefixes for accessories, albeit more limited ones. Have a look at the page I linked, it covers it quite nicely.