Ersatz

By one account, (PROSE: The Dark Path) who fought the Eighth Doctor (TV: Doctor Who) was an "ersatz". (PROSE: The Dark Path)

Behind the scenes
Though barely-explained in The Dark Path, the intention of depicting Gordon Tipple and Eric Roberts' incarnations of the Master as "ersatzes" was to tie in with First Frontier: the intended reveal was that the Tzun had not so much converted into a Time Lord, as they had created a Time Lord clone of him with all his memories. The Master who went on to be executed by the Daleks while thus a duplicate while the original Ainley Master, still in Tremas's Trakenite body, survived elsewhere in the universe.