Redefines   A value of redefines specified for the property string indicates that the association end is redefined with the name specified. This mechanism allows an association end to be recast using a new name and potentially new properties that are more appropriate at any given level of specialization (redefinition).

Explanation

When a class (or any other classifier) is specialized, properties are redefined and made available in the specialized (child) class. These properties will by default have the same name as the properties in the generalized (parent) class. When we specialize a concept we quite often give it a new name and perhaps additional properties even though it represents the same fundamental concept. We see many examples of this in our daily lives; for example where a geometrical figure may be defined at one level as having a perimeter, a specialization of the geometrical figure class could be a circle and the property perimeter could be redefined as circumference.