group stage
noun [ C ] uk/ˈɡruːp ˌsteɪdʒ/ us/ˈɡruːp ˌsteɪdʒ/
（足球或其他体育竞赛的杯赛中的）小组赛阶段
in football and some other sports, the first part of a cup competition when teams are divided into groups and the teams in each group play against each other. The winner or winners of each group then move onto the next part of the competition.
the group stage of the Champions League 冠军杯小组赛阶段