atomic mass unit: Meaning and Definition of

atom'ic mass' u"nit

Pronunciation: [key]
— Physics. Physics.
  1. Also calleda unit of mass, equal to the mass of the carbon-12 atom and used to express the mass of atomic and subatomic particles.
  2. (formerly) a unit of mass, equal to the mass of an oxygen atom having atomic mass 16. Abbr.: amu, AMU
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.