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sem·i·heav·y water(sĕm′ē-hĕv′ē, sĕm′ī-)
A form of heavy water in which the oxygen atom is bound to one atom of hydrogen and one atom of deuterium (heavy hydrogen).
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.