IPA: /ˈæntiˌpoʊp/
KK: /ˈæntiˌpoʊp/
A person who claims to be the pope but is not recognized as such by the official church, often during a disagreement or split in the church.
During the schism, several antipope candidates emerged, each claiming legitimacy.
Antipope → It is formed from "anti-" (meaning against or opposite) and "papa" (from Latin, meaning pope or father). The term refers to a person who claims to be pope in opposition to the legitimately elected pope.
Think of someone who is 'against' ('anti-') the rightful 'father' ('papa') of the church — that's why an antipope is someone who opposes the legitimate pope.