Medical Definition of mass
1: the property of a body that is a measure of its inertia, that is commonly taken as a measure of the amount of material it contains, that causes it to have weight in a gravitational field, and that along with length and time constitutes one of the fundamental quantities on which all physical measurements are based
2: a homogeneous pasty mixture compounded for making pills, lozenges, and plasters <blue mass>
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