Anaesthetic \An`[ae]s*thet"ic\, a. (Med.)
   (a) Capable of rendering insensible; as, an[ae]sthetic agents.
   (b) Characterized by, or connected with, insensibility; as, an an[ae]sthetic effect or operation.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Anaesthetic \An`[ae]s*thet"ic\, n. (Med.) That which produces insensibility to pain, as chloroform, ether, etc.

Source: Webster's Revised Unabridged Dictionary (1913)