Ali, Muhammad Originally Cassius Marcellus Clay, Jr. (kl?) 1942-2016. American prizefighter who won the world heavyweight title in 1964, but was stripped of his title and banned from competing (1967-1970) as a result of his refusal to be inducted into the army during the Vietnam War. He later regained the title two more times (1974, 1978).American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.