also: せいこう
noun
Refers to the exact center of a target, or metaphorically to the crucial point or essence of a matter. Often used in the phrase 正鵠を射る (to hit the mark).
彼の指摘は正鵠を射ている。
His remark hits the mark.
その質問は問題の正鵠
That question gets to the heart of the issue.
From Chinese 正鵠, where 正 and 鵠 both refer to the center of a target. The exact historical derivation is uncertain, but the compound is conventionally associated with the idea of a bull's-eye.