heavy water

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heav·y wa·ter

D2O; water in which the hydrogen atoms are deuterium, or heavy hydrogen (2H), with physical properties that differ noticeably from those of ordinary water; an elevated presence will cause a decrease in metabolic activity; used as a moderator in nuclear reactors because of its capacity to absorb neutrons.
Synonym(s): deuterium oxide
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heavy water

D2O; an isotopic variety of water, esp. deuterium oxide, in which hydrogen has been displaced by its isotope, deuterium. Its properties differ from ordinary water in that heavy water has a higher freezing and boiling point and does not support life.
See also: water
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