C1to accept, admit, or recognize something, or the truth or existence of something: [+ -ing verb]She acknowledged having been at fault.[+ that]She acknowledged that she had been at fault.You must acknowledge the truth of her argument.Historians generally acknowledge her as a genius in her field.[+ obj + to infinitive]She is usually acknowledged to be one of our best artists.They refused to acknowledge (= to recognize officially) the new government.He didn't even acknowledge my presence(= show that he had seen me).The government won't even acknowledge the existence of the problem.Admitting and confessingC1to tell someone, usually in a letter or email, that you have received something they sent you: Please acknowledge receipt of this letter.