What part of no don't you understand? informal sarcastic
I've already said "no" and you still don't understand.
A: Come on, bro! Just lend me your motorbike only one last time. B: What part of "no" don't you understand?
She has politely declined his invitation many times. What part of "no" doesn't he understand?
A way of rejecting an invitation, an idea, or a suggestion
This saying dates back to the late nineteenth century from a song. “What part of no don't you understand? To put it plain and simple, I'm not into one-night stands” (recorded by country music singer Lorrie Morgan, 1992; lyrics by Wayne Perry and Gerald Smith).
Someone who is totally bad at doing something.
Mary really can't sing for toffee.