The *(term) for a system or object describing the fact that _(communication) is as easy as possible for it.

Since _(communication) involves _(marshalling) (aka serializing), portability for an _(object) means that on the systems it's relevant to, that its semantics and their changes can be reliably (which means it's transparent at some level) serialized without loss or distortion. Portability for a <em>system</em> then is just the portability for all of its objects.