A large number of people; many people gathered or involved in an event or situation.
大人数での食事は事前に予約した方がいい。
For dining with a large group, it's better to make a reservation in advance.
このイベントは大人数が集まる見込みだ。
This event is expected to draw a large crowd.
大人数だと意見の調整が難しくなることがある。
When there are many people, it can become difficult to coordinate opinions.