any sort of minor event which causes a nerd to flip out, freak out, or generally over-react. the rest of the non-nerd population usually remains quite calm and unaffected by a nerdtastrophe
A trip, typically to a technical conference in the field of one's employment or to a convention of a nerdy/geeky persuation, that one enjoys on an intellectual level as much as a vacation for general relaxation.
That week-long trip to the photovoltaic conference in Germany was the best nerdcation I've had in years!