The abbreviation "t2" is used to refer to Tech 2 modules.
Advanced versions of "basic" ships and modules. Items with better stats than Tech 1 items, and much higher skill requirements. These items have an orange "II" in the corner of their icon. T2 generally refers to modules rather than ships: a "t2 battleship" refers to a plain battleship fitted with tech 2 modules, and t2 ships are referred to by their type (i.e., "Heavy Assault Cruisers," not "T2 Cruisers").
With actual Tech 2 Battleships in game, this is a bit of an odd example, as it could be a T2 fit BS, or a T2 BS.