1. In scientific usage, the product of the force of gravity, defined internationally as 9.80665 m/s2, times the mass of the body. 2. In common usage, the apparent mass of a body when measured in air by comparison to standard masses of prescribed composition, the effects of the buoyancy of air being ignored. 3. A piece of material, usually metal, of known mass, used as a comparison object in weighing. 4. In statistics, a procedure to assign differential importance to certain observations at the expense of others, or a numerical factor employed in applying such a procedure.