- The definition of a mass defect is the mass of an atom minus the masses of all the individual neutrons and protons in its nucleus.
An example of a mass defect is a number expressed in atomic mass units.
mass defect definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Physics the difference between the mass of an atom and the sum of the masses of the individual neutrons and protons in its nucleus, expressed in atomic mass units
mass defect definition by American Heritage Dictionary
The amount by which the mass of an atomic nucleus is less than the sum of the masses of its constituent particles. Also called mass deficiency.