knock something on the head
From Longman Dictionary of Contemporary Englishknock something on the headknock something on the headBritish English informalPREVENT to stop something happening We wanted to go for a picnic, but the rain’s knocked that on the head. → knockExamples from the Corpusknock something on the head• Fortunately they didn't knock me on the head or anything which they could have done, couldn't they?