n. (plah-yah dust) Dried, packed, and ground up alkali lake bed dust, specifically from Black Rock Desert, NV. It's an unpopular souvenir from Burning Man that gets into everything. So miniscule are its particles that you'll be getting them out of whatever you bring for years to come. No means known yet to man is effective for completely removing this substance from items that have been to the event; all attempts to do so will merely end in utter frustration.
Man 1: What the hell is all this powder on these chairs?
Man 2: I took 'em to Burning Man, fuck, 3-4 years ago. That's playa dust, gets into everything, never comes out.