Slowing. It means there is a mild slowing of the electrical conduction in a certain part of your heart. In most cases it is an incidental finding and not worrisome.
BBB. The heart has a conduction system for its electrical impulses. There are three main branches, the right and the left anterior and left posterior branches. An incomplete right bundle branch block is a slowing in the right bundle conduction but not a loss of conduction in it. It has little clinical significance.