knock oneself out
idiomDefinition of knock oneself out
1
: to cause oneself to become unconscious
He hit his head against the table when he fell and knocked himself out.
2
informal
: to make oneself very tired by doing work
I knocked myself out to get the job done on time.
3
US
—used to tell someone to go ahead and do something "Do you mind if I use this exercise machine first?" "Knock yourself out."