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 converted into a Time Lord but merely created a Time Lord clone of him with all his memories, this being the Master who went on to be executed by the Daleks while the original Ainley Master, still in Tremas's Trakenite body, survived elsewhere in the universe.