Pear-shaped
British SlangDefinition
British slang: describes a plan or situation that has gone badly wrong or failed, often unexpectedly.
Examples
"The demo was fine in rehearsal, but as soon as the investors arrived, it all went pear-shaped."
"Our weekend getaway went pear-shaped when the car broke down on the M25."
"The match plan looked solid until the red card; after that, everything went pear-shaped."