Titanium Ore is a metal ore found only in Northrend.
Titanium is used to craft a variety of items for various professions.
As an ingredient
Titanium Ore can be prospected (consuming 5 ore) with a Jewelcrafting skill of 450, resulting in random uncommon, rare, or possibly epic gems. Each uncommon gem has a 25% chance of appearing, each rare 4% and each epic 5%.
Titanium in WoW is almost certainly a play on the name similarity to the Titans in the game's mythology, which interestingly enough, is not too far from the truth in the naming of Titanium, although the Greco-Roman Titans were used instead.