Source : Webster's Revised Unabridged Dictionary (1913)

Analgesia \An`al*ge"si*a\, n. [NL., fr. Gr. 'analghsi`a; 'an
   priv. + 'a`lghsis sense of pain.] (Med.)
   Absence of sensibility to pain. --Quain.

Source : WordNet®

analgesia
     n : absence of the sense of pain without loss of consciousness