The Collaborative International Dictionary of English v.0.48:

Dizziness \Diz"zi*ness\, n. [AS. dysigness folly. See Dizzy.]
   Giddiness; a whirling sensation in the head; vertigo.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dizziness
    n 1: a reeling sensation; a feeling that you are about to fall
         [syn: dizziness, giddiness, lightheadedness,
         vertigo]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "dizziness":
   abscess, addleheadedness, addlepatedness, ague, anemia, ankylosis,
   anoxia, apnea, asphyxiation, asthma, ataxia, atrophy, backache,
   bleeding, blennorhea, cachexia, cachexy, chill, chills, colic,
   constipation, convulsion, coughing, cyanosis, diarrhea, dropsy,
   drunkenness, dysentery, dyspepsia, dyspnea, edema, emaciation,
   fainting, fatigue, fever, fibrillation, flux, giddiness, growth,
   hemorrhage, high blood pressure, hydrops, hypertension,
   hypotension, icterus, indigestion, inflammation, insomnia, itching,
   jaundice, labored breathing, lightheadedness, low blood pressure,
   lumbago, marasmus, muddleheadedness, nasal discharge, nausea,
   necrosis, pain, paralysis, pruritus, puzzleheadedness, rash, rheum,
   sclerosis, seizure, shock, skin eruption, sneezing, sore, spasm,
   spinning head, swimming, tabes, tachycardia, tumor, upset stomach,
   vertiginousness, vertigo, vomiting, wasting, wooziness