( informal ) to be sth that sb is responsible for or knows a lot about :
Don't ask me about it—that's her department.
( informal ) to be sth that sb is responsible for or knows a lot about :
Don't ask me about it—that's her department.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005