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. Cf. Eötvös experiment, inertia (def. 2a), gravitational mass.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.