Hygienic macros (was: do...until wisdom needed...)

[Brett g Porter]

"Neil Hodgson" <neilh at scintilla.org> wrote in message
news:WF4D6.14028$W7.78315 at news-server.bigpond.net.au...
>    The right way forward for hygienic macros seems to me to be to do a
proof
> of concept implementation on top of standard Python so we can play with it
> and find if there is anything that really needs it.

Hi -- for the non-LISP-ers among us -- could someone give a précis on what
makes a macro 'hygienic'? A quick Google search turned up tons of links, but
none that were explanatory (at least not to a non-LISP programmer like
myself), and ESR's Jargon File doesn't cover it.