former prime minister; ex-premier
Refers to a person who has previously served as prime minister, especially the one immediately preceding the current officeholder. Often used in news and political contexts.
The former prime minister held a press conference.
The current prime minister said they would continue the policies of the previous prime minister.
Compound of 前 (zen, 'previous') and 首相 (shushō, 'prime minister'). A straightforward Sino-Japanese word.