Gendering is the process of associating something with one gender or another. When the process of gendering has taken effect, the thing (many things can be subjected to gendering) has become gendered. It has become associated with one gender or the other.
In most cultures of the world, if not all, various objects and various behaviors are gendered. In other words, they are associated with one gender. These are not necessarily natural associations. Instead, they are associations that are created by society and that can differ from one society to another. In the United States, for example, any skirt or skirt-like piece of clothing is associated with the female gender. By contrast, a kilt in Scotland is not associated with femaleness nor is a lava-lava in Polynesia. Behaviors can also be gendered. In some countries, smoking is seen as a male thing to do. In the United States, caring for children (as in a daycare) is a female activity. These things become gendered through the process of gendering.
Gendering, then, is the process by which a society associates a particular thing or behavior with one gender or another. When enough of society accepts this process, the thing is gendered in that society.