The definition of inbound is something that moves inward. An example of inbound is the freeway that goes toward the city center. 1  traveling or going inward.  Basketball inbounds.
Mass is a measurement of how much matter is in an object. Mass is a combination of the total number of atoms, the density of the atoms, and the type of atoms in an object. How to Measure Mass.
The quantity of matter in a body. The inertial mass is the mass as a measure of resistance of a body to changes in its motion, and the gravitational mass is the mass as a measure of the attraction of one body to another. The general theory of relativity shows inertial and gravitational mass are equivalent.