What is distilled or freeze-concentrated mead called?
It's called honeyjack when freeze distilled. I haven't seen any specific name for steam distilled mead, so it's likely fine to use the same name for both products.  


  Mead can also be distilled to a brandy or liqueur strength. A version called "honey jack" can be made by partly freezing a quantity of mead and straining the ice out of the liquid (a process known as freeze distillation), in the same way that applejack is made from cider. Wikipedia: Mead: Varieties


Unfortunately there are a number of "honey brandies" and "honey liqueurs" that are simply other liquor bases with honey added for flavor and sweetness.

Also, see the discussion on Homebrewing Stack Exchange