sclerosis (skleer-oh-sis) n. hardening of tissue, usually due to scarring (fibrosis) after inflammation or to ageing. It can affect the lateral columns of the spinal cord and the medulla of the brain (amyotrophic lateral s. (ALS) or Lou Gehrig's disease), causing progressive muscular paralysis (see motor neurone disease). See also arteriosclerosis, atherosclerosis, multiple sclerosis, systemic (sclerosis), tuberous (sclerosis).

scle·ro·sis / skləˈrōsis/ • n. Med. abnormal hardening of body tissue. ∎ see multiple sclerosis. ∎ fig. excessive resistance to change: the challenge was to avoid institutional sclerosis.

sclerosis Degenerative hardening of tissue, usually due to scarring following inflammation or as a result of ageing. It can affect the brain and spinal cord, causing neurological symptoms, or the walls of the arteries.