1) Agents that are capable of inducing a total or partial loss of sensation, especially tactile sensation and pain. They may act to induce general anesthesia, in which an unconscious state is achieved, or may act locally to induce numbness or lack of sensation at a targeted site.

2) Substances that cause loss of feeling or awareness. Local anaesthetics cause loss of feeling in a part of the body. General anaesthetics put the person to sleep.