Implied weight is weight that is suggested by an object rather than the object actually having that perceived weight. Works in two dimensions often feature objects that weigh more than the actual weight of the paint and canvas. With all of these people in this painting, as well as the other aspects of the scene, the implied weight would be measured in tons rather than the few pounds that the painting actually weighs.
Most works in three dimensions have actual weight that is consistent with what it appears to be. A building that is made from stone has an actual weight that is clearly perceived. However, a building that has a stone veneer would have an actual weight that differs from its implied weight. The perceived weight would seem to be the same as the building that was made of solid stone. The concept of visual weight is an important element in helping to determine whether a work has symmetry or asymmetry.