in/under no circumstances

in no circumstances

Never; in no case or situation; irrespective of events or conditions. In no circumstances are you allowed to drive home after you've had more than one drink! I'm sorry for my sudden resignation, but in no circumstances will I work for some sexist manager like him.
See also: circumstance

under no circumstances

 and not under any circumstances
Fig. absolutely never. Andy: Under no circumstances will I ever go back there again! Rachel: Why? What happened? Sue: Can I talk you into serving as a referee again? Mary: Heavens, no! Not under any circumstances!
See also: circumstance

in/under no circumstances

used to emphasize that something should never happen or be allowed: Under no circumstances should you lend Paul any money.Don’t open the door to strangers in any circumstances.
See also: circumstance

under no circumstances

In no case; never.
See also: circumstance