any gas or drug used to create a state of unconsciousness or insensitivity to pain.

An impairment or loss of sensation, usually of touch but sometimes of the other senses, that is often part of conversion disorder.

A field of medicine involving the administration of drugs that produce a loss of consciousness or sensation. The term also means a drug-induced state of lack of feeling. This may affect the entire body (as in general anaesthesia), a region of the body (as in regional anaesthesia), or a small amount of tissue (as in local anaesthesia).

absence of sensation (general anaesthesia refers to a state of drug-induced loss of consciousness)