D defs.my
Entry 1 sense Webster, 1913

Antipope

· An·ti·pope · IPA /ˈæntiˌpoʊp/
01 n. One who is elected, or claims to be, pope in opposition to the pope canonically chosen; esp. applied to those popes who resided at Avignon …
  1. 1.
    One who is elected, or claims to be, pope in opposition to the pope canonically chosen; esp. applied to those popes who resided at Avignon during the Great Schism.