To sustain a serious yet insidious injury. The victim is unaware until informed by others.
The Wizard of Oz refers to "the kitchen took a slitch" which means the whole house was lifted off the ground and thrown right back to the ground after traveling some distance, (whether a real or imagined distance), by a tornado, and the extent of the damage is not really appreciated until the munchkins sing about it. "The kitchen took a slitch". During the movie, we assumed that the kitchen, in Dorothy's house was just fine, even though it had sustained the damage caused by a tornado. After all, we are American Movie Fans, and we leave our logical brains at the door. Most of us never even heard the reference to "slitch" nor, if we did hear and understand that word, nor did we ever suscribe this element of insidiousness to it, if we did understand what "slitch" meant.