< programming > A property of a data-object that can exist in many shapes and sizes, but not simultaneously; which distinguishes it from a union . It is often implemented as a set of classes (or structs) derived from a common base class (or with a common header, as in the case of structs), typically without any method s.
It has been loosely described as polymorphic data.
[Clarification?]
(1996-01-07)