adj gone wrong. Usually it’s meant in a rather jovial sense, in a similar way to the American expression “out of kilter” or “off kilter”: Well, I was supposed to have a civilised dinner with my mates but we had a few drinks and it all went a bit pear-shaped. You would be less likely to see: Well, she went in for the operation but the transplant organ’s been rejected and the doctor says it’s all gone a bit pear-shaped. Possible derivations involve glass-blowing or hot-air ballooning. Separately.