inertial mass

noun Physics.
  1. the mass of a body as determined by the second law of motion from the acceleration of the body when it is subjected to a force that is not due to gravity.
  2. the measure of the property of inertia.Compare Eötvös experiment, inertia(def 2a), gravitational mass.
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British Dictionary definitions for inertial mass

inertial mass

noun
  1. the mass of a body as determined by its momentum, as opposed to gravitational mass. The acceleration of a falling body is inversely proportional to its inertial mass but directly proportional to its gravitational mass: as all falling bodies have the same constant acceleration the two types of mass must be equal
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