From Longman Dictionary of Contemporary Englishbe under the impression (that)be under the impression (that)to believe that something is true when it is not I’m sorry, I was under the impression that you were the manager. → impression
Examples from the Corpus
be under the impression (that)• The average American is under the mistaken impression that wildlife refuges have been set up to protect animals.• I was under the impression that you couldn't get a parking ticket on private property.• I was under the impression that people who rented council houses would have to pay the new council tax in addition to their rents.• I was under the impression that we shared certain things equally.• She must be under the impression it was him.• Because alcohol is a central nervous system depressant, many people are under the impression that it improves sleep.• My own service was under the impression that it had the huntin' and shootin' rights in this country.• Both Halle and Sethe were under the impression that they were hidden.• They were under the impression that all strike offenses had to be violent or serious.• She seemed to be under the impression more guests were coming, but nobody else ever came. 