専せん一いち

na-adjective, noun

exclusively; with utmost care

Rare literary word meaning to do something wholeheartedly, exclusively, or with the best care. Often used in the adverbial form 専一に.

• 彼かれは研けん究きゅうに専せん一いちに打うち込こんだ。

  He devoted himself exclusively to his research.

• 病びょう人にんの看かん護ごに専せん一いちな心こころがけが必ひつ要ようだ。

  One must have a mindset of taking the best care when nursing the sick.