Existing in title or name only; nominal; having the title to an office or dignity without discharging its appropriate duties; as, a titular prince
of or associated with or bearing a title signifying status or function; "titular dignitaries" derived from a title; "performed well in the titular (or title) role"; "the titular theme of the book" of or associated with or bearing a title signifying nobility; "of titular rank" of or relating to a legal title to something; "titulary rights
A titular job or position has a name that makes it seem important, although the person who has it is not really important or powerful. He is titular head, and merely signs laws occasionally. = nominal. titular head/leader/monarch etc someone who is the official leader or ruler of a country but who does not have real power or authority (titulus; TITLE)
An episocopal see which has no resident bishop but serves (regardless whether it has a cathedral) as title of a nominal, not pastoral, diocese ((arch)bishopric), for a titular bishop or for an titular archbishop (in which case it's a titular archiepiscopal see)
Most titular sees are defunct dioceses from the Roman empire days, mainly in presently mainly Muslim countries: Turkey, the Levant and Northern Africa.