foam pie
noun [ C ] UK uk/ˌfəʊm ˈpaɪ/ us/ˌfoʊm ˈpaɪ/
泡沫饼（盛在纸盘上的泡沫剃须膏等类似物体，用来扔到其他人脸上作为玩笑或抗议）
an amount of shaving foam on a paper plate, etc. that is thrown at someone's face to make people laugh or as a protest
He was attacked by a protester with a foam pie. 他被一名抗议者用泡沫饼攻击。