All those present; everyone concerned (often used in formal statements or group greetings).
代表は会の成功を祈り、一同頷いた。
The representative wished for the success of the meeting, and everyone nodded.
開店にあたり、一同より感謝申し上げます。
On the occasion of the opening, all of us express our gratitude.
出席者一同で写真を撮った。
All the attendees took a photo together.