Meaning of SLACK in English
(NOT ACTIVE) [adjective] - showing a lack of activity; not busy or happening in a positive wayBusiness is always slack at this time of year.The company is to axe 184 jobs because of slack demand for its products.(disapproving) Discipline in Mr Brown's class has become very slack recently.(disapproving) The auditors also found slack procedures in cash offices.(disapproving) The job is taking a long time because the workmen are so slack.
Cambridge English vocab. Кембриджский английский словарь. 2012