The most popular dish at the party was a big bowl of seven-layer salad with vegetables, eggs, cheese, and other ingredients.

seven-layer 是由数词 seven（七）和名词 layer（层）组成的复合形容词，中间用连字符连接。seven 表示数量"七"，layer 指"层次、分层"。seven-layer 合起来表示"七层的"，用来描述由七种不同食材分层堆叠而成的沙拉。