flat back four
noun [ C usually singular ] specialized uk/ˌflæt bæk ˈfɔːr/ us/ˌflæt bæk ˈfɔːr/
（足球比赛中）四名防守队员平行站位
in football, a group of four defenders who stay in a straight line across the pitch
Playing with a flat back four involves pressing and defending as a unit. 采用四后卫平行站位的打法要求作为一个整体共同进退。