A term meaning "to go to hell in handbasket" or "when the shit hits the fan." Reportedly of British or Cockney origin, from the Royal Air Force'
s description of circular flight paths gone awry, or "pear-shaped."
Also
may relate to a
popular French Revolution caricature of "citizen King" Louis-Philippe, drawn by Honore Daumier and Charles Philipon in 1832 as a jowly pear. The
French term "poire," or pear, was slang for "fool" or "idiot" - and soon thereafter, all caricatures of the King were banned, pear-shaped or not.
"To say that it all goes
pear-shaped is an under statement. The reactors go out of
control and quickly the effort is not to save the
plant, but to minimise the effects."