expression
single-handedly; alone; on one's own
A yojijukugo meaning to undertake something entirely by oneself, without any assistance. Often used in contexts of solitary effort or independence.
彼は単槍匹馬で新事業を立ち上げた。
He single-handedly launched the new business.
単槍匹馬で敵陣に乗り込む覚悟だ。
He is prepared to charge into the enemy camp all alone.
A yojijukugo of Chinese origin, literally 'single spear, lone horse', evoking the image of a lone warrior charging into battle. The exact historical derivation is uncertain, but the phrase is conventionally associated with solitary, unaided action.