( informal , often disapproving ) to be confident that you know sth, especially when you actually do not :
He thinks he knows all the answers.
( informal , often disapproving ) to be confident that you know sth, especially when you actually do not :
He thinks he knows all the answers.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005