The act of causing rapid evacuation of a room or other confined space by floating a particularly nasty air biscuit. Most commonly, a grierson requires the assistance of a tarka for maximal effect. The word is derives from the name of a rotund large-eared red-headed gentleman scholar of an unathletic nature (not to be confused with a waby), who claimed to be able to clear the audience of a 300-seat lecture theatre in 10 seconds.
From the Philadelphia Enquirer, 23rd March 2004: Mass panic ensued after shouts of "grierson, grierson" were heard in the darkened room. Firemen with breathing apparatus recovered the bodies of 18 of the deceased several hours later.
The new metric unit of aerial noxiousness. Most commonly applied to the scientific quantification of odious flatulence. Defined by the radius of devastation: 10 centigrierson (cGr) will eliminate 50% of sentient life forms within a 1 metre radius. Named after the now notorious scholar, Grierson, who continued to consume numerous plates of tarka despite clear medical advice. The US unit, the air biscuit, is equivalent to 18.4567cGr.
The CIA today reported that Iran has developed a new weapon that will kill but leave buildings undamaged. The weapon, with a 10 kilogrierson yield, was tested in the Dasht-e Kavir desert region. Satellites recorded a zone of devastation with a radius of 25km and the consequent mass evacuation of the town of Garmsar. Reuters, 28th June 2006.