The act of piercing the center of a cake with a thin (usually paring) knife to see if the cake is done. If the knife comes out clean, it’s done. Hooray! If it comes out with batter clinging to it, it isn’t done. Be patient and put it back in the oven. This can also be done with a toothpick or skewer, but I rarely have those on hand, so knives it is.