Not in a million years.
[Idiom] NOT IN A MILLION YEARS. - Unlikely Choices and Events in American English
Never
When you hear someone say 'Not in a million years,' they are expressing an extreme improbability or outright refusal. Imagine you ask your friend if they plan on skydiving tomorrow, and they respond with 'Not in a million years.' What they mean is that there’s virtually no chance they'll do it - it’s that unlikely. It’s as if they are saying that even if given a million years to consider it, their answer would still be no. This idiom is commonly used to emphasize a strong disbelief in something happening or a firm decision against participating in an act.
Example Sentences
Not in a million years did I think he'd win the lottery.
I never expected he would win the lottery.
She said not in a million years would she go bungee jumping.
She firmly refused to go bungee jumping.
Not in a million years did I expect him to return.
I never expected him to come back.