- adj. phr.Busily doing something; active.
His rule for success was to keep always at it.
The couple who owned the little cleaning shop were at it early and late.
Mr. Curtis heard a loud crash in the next apartment - the neighbors were at it again.
Словарь американских идиом. — СПб., Изд-во "Лань". Оригинал: A.Маккей, М.Т.Боткер, Дж.И.Гейтс. 1997.