/ Dictionary / Index A amyotrophic lateral sclerosis: Meaning and Definition of Find definitions for: a•my•o•troph'ic lat'eral sclero'sis Pronunciation: (ā"mī-u-trof'ik, -trō'fik, ā-mī"u-), [key] — Pathol. Pathol. an incurable disease of unknown cause in which progressive degeneration of motor neurons in the brain stem and spinal cord leads to atrophy and eventually complete paralysis of the voluntary muscles. Abbr.: ALS Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. amyotonia Amytal Related Content Daily Word Quiz: candid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language