apply firm pressure to the surface of (something), using a repeated back and forth motion

she rubbed her arm, where she had a large bruise

he rubbed at the earth on his jeans

(with reference to two things) move or cause to move to and fro against each other with a certain amount of friction

many insects make noises by rubbing parts of their bodies together

the ice breaks into small floes that rub against each other

an act of rubbing

she pulled out a towel and gave her head a quick rub

the central problem or difficulty in a situation

that was the rub—she had not cared enough

(in bowling) an uneven patch of ground that impedes or diverts a bowl