Numb is an adjective that has two meanings: unable to feel physical sensations, and without emotion. It is also a verb that means to remove the ability to feel sensation, either physically or emotionally.
After Jane got anesthesia at the dentist's office, her lips were numb.
Max was numbafter receiving the news of his father's sudden death.
The anesthetic cream numbedArthur's finger.
The shock numbedRebecca's emotions.
You know that feeling when your leg goes numb, often because you don't move it for a while? In English we say that a body part "is asleep" or "fell asleep." The sensation can also be called "pins and needles." For example, "When I sit on the floor for too long, sometimes my foot falls asleep." Or, "When I feel pins and needles in my leg, I try to stand up and walk around until the sensation goes away."
be numb to sth: not be affected by something. Example: "There's no point in making fun of me. I'm numb to your insults!"