The Collaborative International Dictionary of English v.0.48:

Anaesthetic \An`[ae]s*thet"ic\, Anesthetic \An`es*thet"ic\
   ([a^]n`[e^]s*th[e^]t"[i^]k), a. (Med.)
   (a) Capable of causing anesthesia; as, an[ae]sthetic agents.
   (b) Characterized by, or connected with, anesthesia; as, an
       an[ae]sthetic effect or operation.
       [1913 Webster + AS] anesthetic

The Collaborative International Dictionary of English v.0.48:

anaesthetic \an`[ae]s*thet"ic\, anesthetic \an`es*thet"ic\--AS,
   n. (Med.)
   A substance which produces anesthesia, as chloroform, ether,
   etc.
   [1913 Webster + AS]

The Collaborative International Dictionary of English v.0.48:

Anesthesia \An`es*the"si*a\, n., Anesthetic \An`es*thet"ic\, a.
   Same as An[ae]sthesia, An[ae]sthetic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

anesthetic
    adj 1: relating to or producing insensibility [syn:
           anaesthetic, anesthetic]
    2: characterized by insensibility; "the young girls are in a
       state of possession--blind and deaf and anesthetic"; "an
       anesthetic state" [syn: anesthetic(a), anaesthetic(a)]
    n 1: a drug that causes temporary loss of bodily sensations
         [syn: anesthetic, anaesthetic, anesthetic agent,
         anaesthetic agent]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "anesthetic":
   Mickey Finn, Pentothal, alleviating, alleviative, analgesic,
   anodyne, assuasive, balmy, balsamic, benumbing, cathartic,
   chloroform, cleansing, cocaine, deadening, demulcent, dope, drug,
   dull, dulling, easing, emollient, ether, ethyl chloride, ethylene,
   gas, hard, hypnotic, impassible, impenetrable, impermeable,
   impervious, insensate, insensitive, knockout drop, lenitive,
   lullaby, mandrake, menthol, mitigating, mitigative, morphia,
   morphine, narcotic, nightcap, nitrous oxide, numbing, obtuse,
   opiate, opium, pain-killer, pain-killing, palliative, poppy,
   purgative, relieving, remedial, rocky, sedative, sleep-bringer,
   sleep-inducer, sleep-producer, sleeping pill, softening,
   somnifacient, soothing, soporific, stunning, stupefying, subduing,
   tranquilizer