Vicar of Christ (from Latin Vicarius Christi) is a term used in different ways and with different theological connotations throughout history. The original notion of a vicar is as an "earthly representative of Christ", but it is also used in the sense of "person acting as parish priest in place of a real person."[1] The title is now used in Catholicism to refer to the bishops,[2] and more specifically, was historically used to refer to the Bishop of Rome (the pope).
Lumen gentium
was invoked but never defined (see the help page).