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1.
A person cool enough to invite to MND, THD, WND, ThND and/or FND.

Tossers who can only talk about work or their kids are definitly NOT xND proof.
You'd better not invite them again, but if you find yourself in a pub with a non-xND proof person, you can always

pull a Zewald.
Good to finally have met X, he's xND proof for sure!
by YoungR October 19, 2010