Source : Webster's Revised Unabridged Dictionary (1913)

Sclerosis \Scle*ro"sis\, n. [NL., fr. Gr. (??, fr. sklhro`s
   hard.]
   1. (Med.) Induration; hardening; especially, that form of
      induration produced in an organ by increase of its
      interstitial connective tissue.

   2. (Bot.) Hardening of the cell wall by lignification.

   {Cerebro-spinal sclerosis} (Med.), an affection in which
      patches of hardening, produced by increase of the
      neuroglia and atrophy of the true nerve tissue, are found
      scattered throughout the brain and spinal cord. It is
      associated with complete or partial paralysis, a peculiar
      jerking tremor of the muscles, headache, and vertigo, and
      is usually fatal. Called also {multiple, disseminated, or
      insular, sclerosis}.

Source : WordNet®

sclerosis
     n : any pathological hardening or thickening of tissue [syn: {induration}]
     [also: {scleroses} (pl)]