Jack Robinson
noun old-fashioned uk/ˌdʒæk ˈrɒb.ɪn.sən/ us/ˌdʒæk ˈrɑː.bɪn.sən/
before you can/could say Jack Robinson 突然间，一眨眼工夫；说时迟那时快
used to refer to something being done or happening very quickly
I put the dish of food on the floor, and before you could say Jack Robinson, the dog had eaten it. 我刚把那盘食物放在地上，狗一下子就吃掉了。