A rub is a small scratch or mark on the skin that might feel sore.
When you get a bruise or scuff on your knee or elbow, you might notice it starts to form a red or purple "rub". This happens when blood comes up to the surface of the skin. You can also use "rub" to talk about something that's been worn down by rubbing against something else - like a rope getting worn away from constant friction with a rock.
An act of rubbing.
Example: Give that lamp a good rub and see if any genies come out.
