The Collaborative International Dictionary of English v.0.48:

Asphyxiation \As*phyx`i*a"tion\, n.
   The act of causing asphyxia; a state of asphyxia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

asphyxiation
    n 1: the condition of being deprived of oxygen (as by having
         breathing stopped); "asphyxiation is sometimes used as a
         form of torture" [syn: suffocation, asphyxiation]
    2: killing by depriving of oxygen [syn: suffocation,
       asphyxiation]

Moby Thesaurus II by Grady Ward, 1.0:

92 Moby Thesaurus words for "asphyxiation":
   abscess, ague, anemia, ankylosis, anoxia, apnea, asphyxia, asthma,
   ataxia, atrophy, backache, bleeding, blennorhea, burking, cachexia,
   cachexy, chill, chills, choke, choking, colic, constipation,
   convulsion, coughing, cyanosis, diarrhea, dizziness, dropsy,
   drowning, dysentery, dyspepsia, dyspnea, edema, emaciation,
   fainting, fatigue, fever, fibrillation, flux, garrote, growth,
   hemorrhage, high blood pressure, hydrops, hypertension,
   hypotension, icterus, indigestion, inflammation, insomnia, itching,
   jaundice, killing, labored breathing, liver death,
   low blood pressure, lumbago, marasmus, megadeath, nasal discharge,
   nausea, necrosis, pain, paralysis, pruritus, rash, rheum,
   sclerosis, seizure, serum death, shock, skin eruption,
   smotheration, smothering, sneezing, sore, spasm, starvation,
   stifling, strangling, strangulation, suffocation, tabes,
   tachycardia, throttling, tumor, upset stomach, vertigo,
   violent death, vomiting, wasting, watery grave