Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

dizziness
     n : a reeling sensation; feeling about to fall [syn: {giddiness},
          {lightheadedness}, {vertigo}]