A four-character idiom meaning to be of one heart and body; to share identical feelings or purpose—used to emphasize unity or strong bond.
新しいプロジェクトではチーム全員が一心同体で取り組んだ。
For the new project, the whole team worked as one.
夫婦は一心同体となって家庭を支えている。
The married couple supports the household as one.
選手と監督が一心同体で戦った試合だった。
It was a match where the players and coach fought as one.