It means that instead of cutting or topping your plant you instead take the top stalk and pinch it hard between your thumb & forefinger. You can bend it as well 90 degrees. I have done this with the result being the lower branches fill out while you reatin the top cola. I have done this after having topped - I pinch the two branches that result from the topping, giving me fuller lower branches with more bud sites and two colas. It's an art, not a science. You can't pinch so hard you break the stem; you just want to debilitate it a bit so the plant sends energy to other areas of the plant.