From Longman Dictionary of Contemporary Englishnot believe/think/do something for a/one momentnot believe/think/do something for a/one momentespecially spokenDON'T THINK SO/DOUBT IT used to say that you did not believe, expect etc something at all He didn’t fool me for a moment. She had never for one moment imagined that it could happen to her. → moment
Examples from the Corpus
not believe/think/do something for a/one moment• His leader did not believe for one moment the protestations of innocence.• I do not concede for a moment that this is a devolution measure.• His hand had not wavered for a moment.• Neither team will half-step, not even for a moment.• I would not suggest for one moment that they existed here. 