It's used to mean that the placement of the lower level components - vertices, edges and faces - are well aligned to the higher level structure of the object, and make up a well defined 2D grid that flows along the models surface. In particular you'd want edges going along/perpendicular to mesh structures such as limbs, and around facial features and other details in a logical manner.
Otherwise when applying deformations as part of an animation the model will not have the detail in the right places to still look good, e.g. if there is no edges perpendicular to a joint in a limb, the bent version of the limb cannot have a clear smooth line along the joint, and the edges and faces become janky.
Under this definition, marching cubes cannot produce good 2D topology, as the mesh features are all aligned to the cardinal grid instead of the features of the object represented.