From Longman Dictionary of Contemporary Englishnot hear/understand/believe a wordnot hear/understand/believe a wordNONE/NOTHINGused to emphasize that you cannot hear, understand etc what someone says or writes No one could hear a word because someone had cut the amplifier cable.not hear/understand/believe a word of I can’t understand a word of Russian. → word
Examples from the Corpus
not hear/understand/believe a word• However, it also shows that they are not very useful, for Hera did not believe a word of it.• For the rest of the journey Maria prattled on about Bradford, but Ruth did not hear a word.• Do not believe a word of it.• We had not heard a word about my father all this time.• To date I've not heard word one about such a plague in the Czech Republic.• I kept it up until I was certain you were not hearing a word. 