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.