Not for a/one moment Definition 1 of 3Pro Tip 1/3Absolute Certainty Expresses total confidence in what you're saying, with no space for doubt. I trust her completely, not for a moment did I suspect her. Pro Tip 2/3Reinforce Denial Used to make a denial stronger and show that there was never any doubt. Not for a moment did he entertain the falsehoods being spread. Pro Tip 3/3Emphatic Rejection Highlights a strong rejection of a proposal or idea from the start. She dismissed the rumors, not for a moment believing them.