1.
running for office; standing as a candidate
Entering a political election as a candidate. The most common modern use of this word.
市長選挙に出馬する。
To run for mayor.
彼女は来年の国政選挙への出馬を表明した。
She announced her candidacy for next year's national election.
現職の知事が三選を目指して出馬した。
The incumbent governor ran for a third term.
2.
entering a competition; stepping into the fray
More broadly, stepping forward to take on a challenge or competition. Originally referred to riding out to battle on horseback.
社長自ら出馬して交渉にあたった。
The president himself stepped in to handle the negotiations.
今回のプロジェクトには部長が出馬することになった。
The department head will be stepping in for this project.
ベテラン選手が代表戦に出馬する可能性がある。
There is a possibility that the veteran player will enter the national team match.
Literally "riding out on horseback" (出 = go out + 馬 = horse). Originally a military term for riding into battle, now primarily used for political candidacy.
COMMON COLLOCATIONS:
- 選挙に出馬する (to run in an election)
- 出馬を表明する (to announce one's candidacy)
- 出馬を見送る (to decide not to run)
- 出馬要請 (request to run for office)
USAGE NOTE:
In political contexts, 出馬 is the standard word for announcing or entering a candidacy. The extended sense (a senior person personally stepping in) carries a nuance of someone important entering the scene to take charge.