The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. (Bot.) Hardening of the cell wall by lignification.
      [1913 Webster]

   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. Formerly referred to as multiple
      sclerosis, disseminated sclerosis, or insular
      sclerosis, but now usually called only multiple
      sclerosis, or MS.
      [1913 Webster +PJC]