Stagflation
Keynes didn't use the term, but some of his work refers to the conditions most would recognise as stagflation. In the version of Keynesian macroeconomic theory which was dominant between the end of World War II (WWII) and the late-1970s, inflation and recession were regarded as mutually exclusive, the relationship between the two being described by the Phillips curve.  Stagflation is very costly and difficult to stop once it starts.