a·my·o·tro·phic lateral sclerosis 
(ā′mī-ə-trōfĭk, -trŏfĭk, ā-mī′-)
(ā′mī-ə-trōfĭk, -trŏfĭk, ā-mī′-)n. Abbr. ALS
A chronic, progressive disease marked by gradual degeneration of the nerve cells in the spinal cord that control voluntary muscle movement, causing muscle weakness, atrophy, and eventual paralysis. Also called Lou Gehrig's disease.