What it means
Means to stop something completely and be done with it. You use it when a plan, job, conversation, or whole situation needs shutting down rather than dragging on. It can sound practical, fed up, or a bit sharp, depending on how you say it.
Usage examples
"Right, can we knock this meeting on the head? I'm starving and Dave's still waffling. Let's grab a cuppa and sort it tomorrow."
"Let's knock it on the head for tonight, we have been staring at this code for six hours straight."
"They knocked the whole festival on the head when the headline act pulled out last minute."
"If the pub's shut and it's bucketing down, let's just knock it on the head and order a takeaway."
"We tried fixing the boiler for two hours, then Mum said knock it on the head before someone blows the kitchen up."
Where it comes from
This is old British English. It first showed up literally for killing an animal with a blow to the head, then drifted into everyday speech for stopping something outright. By the 1900s people were using it for rows, plans, jobs, and any situation that needed ending properly.
