From Longman Dictionary of Contemporary Englishnot say a wordnot say a worda) (also not breathe a word) to not say anything about something because it is a secretPromise you won’t say a word to anyone?b)to not say anythingWhat’s wrong? You haven’t said a word since you got here. →word
Examples from the Corpus
not say a word• She knew that she could not say a word until she had something.• He did not say a word, just stared at the sky.• She did not say a word.• Williams did not say a word until we got back to the company after the mission.• Yoyo does not say a word.• Marty was offering her his handkerchief, not saying a word.• We sit there for a few more minutesnot saying a word.• Could Sandra pleasenot say a word to anyone, not even the women or the other rescueworkers?