to not pay or do sth at the right time :
They had fallen behind with their mortgage repayments.
He's fallen behind with his school work again.
to not pay or do sth at the right time :
They had fallen behind with their mortgage repayments.
He's fallen behind with his school work again.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005