In email or instant messaging vernacular, to express straight-off-the-boat appreciation of -- or, sardonically, recalcitrant disdain for -- the state of affairs; an homage to Bransonite comrade comedian Yakov Smirnoff.

In use:

StonedWilma says: I just bought a laptop for $200!
RocketSloth_085 says: WAC!

TigerPawz says: Did you hear about the new provisions to the Patriot Act?
EarbudsToo says: ugh
EarbudsToo says: wac