n.two games instead of one (especially in baseball when the same two teams play two games on the same day)
同义词：twin billdouble feature
英汉双解大词典
doubleheader/ˈdʌbəˌlhɛdə/(doubleheaders)
1.
N-COUNT（可数名词）
A doubleheader is a sporting contest between two teams that involves two separate games being played, one after the other, often on the same day. (通常在同一天的)连续的两场比赛 [美国英语]