expression
Fixed adverbial phrase meaning everyone acts together as a single body, often used in contexts of teamwork, solidarity, or collective effort.
社員が一丸となって新プロジェクトに取り組んだ。
The employees worked on the new project as one.
チームが一丸となって優勝を目指した。
The team aimed for the championship united.
From 一丸 (one lump/ball) + となって (becoming), literally 'becoming one ball'. The phrase figuratively expresses people uniting into a single cohesive force.