What is Anaesthesia?

Legal Definition
In medical Jurisprudence.

(1) Loss of sensation or insensibility to pain, general or local, induced by the administration or application of certain drugs such as ether, nitrous oxide gas or cocalue.

(2) Defect of sensation or more or less complete insensibility to pain, existing in various parts of the body as a result of certain diseases of the nervous system.
-- Black's Law Dictionary