slacken

verb
1
to gradually become, or to make something become, slower, less active, etc.
کند شدن, شل کردن, کاهش یافتن, آهسته کردن, سست کردن, کاهش دادن
synonym relax
2
to become, or to make something become, less tight
شل شدن, کم کردن, شل کردن, سست کردن, سست شدن
His grip slackened and she pulled away from him.
He slackened the ropes slightly.
Slacken off the ropes.
synonym loosen