This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 110b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
Section 9.8.4 [namespace.udir] paragraph 3 uses the term extended-namespace-definition three times:
If a namespace is extended by an extended-namespace-definition after a using-directive for that namespace is given, the additional members of the extended namespace and the members of namespaces nominated by using-directives in the extended-namespace-definition can be used after the extended-namespace-definition.I think the intent is clear, but unfortunately I cannot find any other mention (or definition) of this term.
Mike Miller: True enough; in Section 9.8.2 [namespace.def] [the grammar] it's called an extension-namespace-definition.
Proposed Resolution (10/99): Systematically replace "extended-namespace-definition" by "extension-namespace-definition".