Oxygen Free Copper.
The real truth is it is a buzz word used by high-end audio cable manufactures to charge you 3 times what the product is worth.
All it really means is the copper is annealed in an oxygen free enviroment which most is made this way today.
Annealed means the copper is heated then cooled down slowly to prevent the crystalian structure from forming otherwise known as "Soft Drawn" copper. By keeping oxygen out of the process keeps it from bonding to the copper which limits corosion or petina.
