write-in candidate

Từ điển Oxford Advanced Learner 8th

write-in candidate [write-in candidate] BrE NAmE noun (AmE)
a candidate in an election for public office whose name is not printed on the official list of candidates, usually because he or she has not been selected by a political party. People voting for such a candidate must therefore write his or her name on the voting paper. Some use this write-in vote, or write-in, as a form of protest by writing ridiculous names on the voting paper.